Prevent other sellers from seeing products of seller 1

I don't know if this module has a specific rule for that, but in drupal you can do a lot of things to prevent that.

Try creating a view for watching products, with an edit link, and in the pane configuration set visibility to the user who has created items.

Or, in the product template add php code in order to prevent other sellers from seeing that product in ALL the pages (RECOMMENDED but i don't know if products are seen like a teaser too).

I wish i could help you more, but I can't explain things very well in english.
You will find a lot of ways of doing it when you know php and drupal.

I dont think rafinskipg was saying you have to write a module for this. I think with the views module, what you want can be accomplished.

For your customer groups, I think you can just set up different roles and then use views to limit what categories/etc each can see.

That's a good a idea, using roles for viewing products.

GeorgX you can try this.

Open node.tpl.php. (or product.node.tpl.php if exists something like that)

Use php to determine if the logged-in user is the author of the product (or a user with a role that can see the product), if not: use drupal_goto() -redirect function- to prevent the user seeing the product.

$user is the variable to use for the author of the content

$user_obj is the user logged in.

Use this function to determine the role of the user and make redirect

$user_obj = user_load(arg(1));
if (in_array('ROLE1', $user_obj->roles)) {
drupal_goto("page");}

I used the taxonomy term permissions module to make some terms viewable only by admins. Then I apply those terms to some products and filter views on those terms. (I sell memberships, the admin owns those, and I don't want them showing up in some views.)