Remove the ability to post to multiple groups

On a technical level, is this a simple configuration change?

Personally, I'm in favor of this change. I was once guilty of cross-posting but have since seen the light.

The groups that I help manage have had a lot of cross-posting in them (lately I've seen a lot of webinars by firms based in other countries) and it would be good to have this change implemented.

Soon there will be a wicked witch and everything will be changed. Until then we'll continue down the brick road I guess. #2590497: [meta] Proposal to migrate groups into Drupal.org

This has been a long standing annoyance of mine, too. I used to go in and manually edit posts to bring them down to just on-topic groups but it seems like GDO is just being left to grow weeds until the magical change happens so I've stopped bothering. Hopefully whatever is going to happen happens soon because, as it is, GDO is an embarrassment. :(

tl;dr "We need to explore some options and the potential consequences of those options. GDO is a very diverse group. It is not so easy to appreciate how various groups and individuals use GDO."

There are many ppl who do not want the crossposting feature removed.
A brief history lesson is required here.
To date, we have policed these posts and discourage many offenders from blanketing GDO with posts irrelevant for specific groups. Certainly a better job could be done there. However, it is a valuable thing to be able to post announcements and discussions to a broader # of groups when it is relevant.
The policy once was that we couldn't "splinter" groups into smaller groups. Rather than having a separate group for every university in the same state, we encouraged users to tag their posts accordingly. Example. My home of Indiana has Purdue, UI, Notre Dame, Butler & many other notable Higher-Ed orgs. All of the aforementioned orgs are doing something with Drupal. the concern was that if we had many smaller groups they would be less active and less attractive to new members. However...
This didn't prevent the creation of a great many "splinter" groups from being created and not just Higher-Ed groups. Look at Ohio. They have 6 groups, one of which has one member and the group hasn't had a post in over 2 years. The other 5 are fairly well used.
So what then... When the next Ohio Drupal Camp is being discussed [keep in mind the Camp is mobile and be hosted by any city in Ohio] they will most certainly cross post to all Ohio groups. Who knows, it might even wake up the sleepy Akron group.
If we remove the crossposting functionality any or all of the following could be a consequence:
[a] users now posting "pointer" posts on other groups. [EX: hey group "X" here's a link to a post on group "Y" where we're talking about topic "Z" in case you want in on the discussion] OR [hey group "X" here's a link to an event on group "Y" please go to that node to join the conversation"]
[b] many users will not join the other "relevant" groups and will simply remain unaware.

Personally, I'd like to see new subscription options.
Per group you can choose
[a] no notifications from this group [except admin broadcasts]
[b] ALL notifications
[c] Individually select content-types. [some one may choose to only receive EVENT node notifications]
[d] the option to "mute" a conversation thereby no longer receiving notifications from a specific node.
[e] the option to ignore posts that are crossposted?!?! I just thought of this one. Hmmm. This doesn't address the issue that the crosspost still appears on the River Of News for that group. Some may call that clutter.
To be clear... I believe when the Group owner uses the Broadcast feature, all users should receive that notice.

Other options:
[a] A last possibility is that we return to the old-school rules and reduce the number of groups through a process of merging and purging. This will be met with hostility as we deny current OG Node owners of their current privileges.
[b] A button on each crossposted node visible to group admins. "Remove From This Group" Clickin it removes the current group from that node's OG field. Also notifies the owner. [I would prefer that the group admin reach out to the node owner and ASK politely, but hey... Empower the group admins] :-)
[c] Establish a "Strike Count." If you willy-nilly post your legitimate node to 20 groups and many of them complain, a GDO mod will pair it down to the relevant groups and hit a +1 on the user's acct. Only fellow Mods can see this, but we will be better able to keep track of repeat offenders. In extreme cases I suppose we could reduce privileges to repeat offenders.

Yah... this got quite long. It seems clear that we must do something about the crossposting issue. Many are bothered by it and it is a legitimate complaint.

Personally, I would just like to see it limited. There are, as you pointed out, legitimate reasons to crosspost but it's being abused. I think putting a limit on it coupled with wording on the group creation form warning people to limit the post to only relevant groups would help quite a bit. As it is, there is nothing on the discussion creation form that instructs you to limit the groups so people who are using their posts for marketing (like webinars) have no reason to limit them.

Excellent point, Michelle.
You've identified some low hanging fruit which could [should?] be implemented sooner rather than later.
Who can react to these simpler requests and either implement them OR explain why it won't be?

The current state of drupal.org staffing, roadmaps and D8 make even simple changes not really likely. For an even more disheartening example see: #2536122: Push to get the Drupal Organization to update the Drupal forums which also makes clear that volunteer (code) contribution is "encouraged" but pointless.

Yah,
That thread bummed me out long ago.

Well... Now we know what we know.
We can close the conversation and hope for action in the future.
I'll be the first to say that we have bigger concerns right now than crossposting. But it would have been nice to make some simple changes.
Thanks for clarifying and explaining some of this, Dave.

I am in no way speaking for the awesome Assoc staff who are doing a lot of splendid things. I am a mere community member webmastering away on d.o and gdo who is a tad frustrated by the current direction things are taking. Let's celebrate D8 today and hope the staff can focus on the neglected parts of our home afterwards.

The only development done on groups.drupal.org is to replace it. The plan seems to migrate it into drupal.org, as described in #2590497: [meta] Proposal to migrate groups into Drupal.org.