Can Drupal do this?

Drupal will do most, if not all of this.

-Store user information in over 10 different languages.(MySQL)

As far as I know MySQL will store international characters.

-Have search capabilities for that user information.

There is a thread to test an update to the search functionality which will include full support for international characters. http://drupal.org/node/33033

-Associate members’ records geographically.

You should, more than likely, define a geographical vocabulary in the taxonomy. I am not sure how to associate the users to the taxonomy, but you could certainly have them subscribe to a newsletter posted to it.

-Ability for administrators to send emails by geographical areas and areas of interest.

See above suggestion for subscriptions. It is conceivable that you could use the taxonomy to filter users into geographical lists, if you know how to associate users with a taxonomy.

-have multi-lingual bulletin boards, or if possible (I believe it's not possible) one that translates to each particular language set on users profile.

I know some modules have translations, but I am not familiar with their implementation. It is likely that both are possible.

-Allow members their own blogs or web-pages and to sign up their own members.

Definitely. You can let each member have a blog, only certain members (based on user role), or you can define separate sites for each blog author and make him administrator of that with the user roles. Sites can have independent databases, or share the same data.

I don't have links handy, but you should click the handbook tab and start reading through to get a better feel for the capabilities of drupal. The handbook is largely contributed by the community developers who are using drupal to solve complex problems. Depending on whether or not you like to get your hands dirty, I have no doubt that if drupal does not fulfill your requirements, you could extend it to do so and maintain a clean, fast codebase.
_________
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Have a look at http://www.ecademy.com

The site is running Drupal.

It is a very busy site with more than 60000 members.
Speed and performance problems has not been an issue for them.

I do some sites in different languages and the translation module in Drupal is fantastic. It is all done in the web interface. No programming.

There are several mailing lists modules for Drupal and you can define user input of geographical areas etc without programming when you configure the system using the profile module.

To have multi-lingual bulletin boards is clearly possible. Automatic translating is not standard but why not. Just some programming needed. no big deal if you ask me. (Sounds fun)

Allow members their own blogs or web-pages and to sign up their own members is what http://ecademy.com is doing. That is standard with the right configuration.

Feel free to contact me if you want more specific advice.

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Of course it will depend on your budget, as the hardware requirements would be staggering if you are seriously expecting "500,000 could be logged in simultanesouly".

Download the scalability presentation: http://drupal.org/drupalcon-2005-media

And you might want to see what kind of hardware large communities (but much smaller than 500.000 simultaneous) would require (check the bubbles for interviews with some hardware lists): http://www.big-boards.com/

Any web application software written well should be able to handle from the smallest to the largest of uses. My question to you is not that of the CMS, but that of the requirements of your data.

1) Do you plan on using a master/slave sql setup?
2) Is clustering a must?
3) Is the source language important?

MySQL still is not where it should be insofar as master/slave data integrity are concerned (or even failover). Clustering then could present problems. Wikipedia itself does not employ automatic failover of its master/slave mysql servers. And Google solves the problem of data consistency issues by taking its servers offline during the "google dance".

So really, you need to look at your data -- which is probably your biggest asset. If you require 5 9s, then you may want to look at other options such as MSSQL which has a good clustering environment.

Once you decide those fundamentals, then I'd look at the software that supports the tools you require.

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