Is Drupal robust enough to provide functions for Social Networking Sites?

The short answer is "yes", but "Social Networking" means different things to different people so you'll have to do your own research to ultimately determine if Drupal is the right fit for your project. This type of question has been asked 100's if not 1000's of times before so you should be able to find many threads on the subject.

I would suggest you first figure out things like who your target audience is, what will make them keeping coming back, how will they interact, etc. This information will in-turn help identify and drive the features your web site will need.

Good luck!

I am a bit surprised at the question as its not the first time you have asked http://drupal.org/node/458062 and http://drupal.org/node/453568

Dont take it the wrong way, but when i see questions like this my first thought goes to "Student wanting someone to do his coursework" , my reasoning is i get these sort of questions on my own site regularly, and all the information needed is in front of the person raising the question.

The best suggestion I can give is install it and play, see if it does what you want/expect, the only opinion that counts in the end is your own (its how i determined it was suitable for my needs).

There are 188 modules under the category 'community':
http://drupal.org/project/modules?filters=tid%3A56%20drupal_core%3A87&so...

There are 175 modules under the category 'media':
http://drupal.org/project/modules?filters=drupal_core:87%20tid:67&solrso...

There might be other modules you'd be interested in under other categories, that would help foster
a community either directly or indirectly:

User management (153)
Evaluation/rating (58)
Organic Groups (51)
Games and Amusements (30)
Location (57)
Third-party integration (431)
Filters/editors (155)

Learn how to use the faceted search (ie. after searching, lots of options appear in the right side menu)
I also find http://drupalmodules.com a helpful search tool
And I love the usage statistics: http://drupal.org/project/usage

Learning which modules are available and how they are best used is a VERY large part of your first
three or four drupal sites. In order to decide upon 30 modules for my first site, I had to test 100, which
took between 200 and 300 hours. Some modules are small and easy, taking minutes to test. But some
areas like images & media, taxonomy, navigation, permissions, and wysiwyg editors can take many
dozens of hours to research and test.

With so many modules, combinations of modules, permutations of module settings, module strengths
and weaknesses, and to a lesser extent module bugs and compatibility issues, I hope you can appreciate
why you're perhaps not getting the desired, straight-forward answer to your question.

Please don't post duplicate threads. I've deleted the one dupe that didn't have any replies yet. Thanks.