Check out the stats: http://www.cdc.gov/std/stats/

Now, you may think that the student population at MIT is special, and it is: just like any other college, the infection rates are higher. Take herpes, for instance - we're talking 10%, yep. Think of three friends. If each of them thinks of another two friends, you can bet that one of y'all has herpes.

If you think that school is stressful, imagine having an std, to top that. Use condoms! They are well known, by design and countless empirical studies, to greatly reduce the chances of infection. The MIT Community Wellness Center makes them available for free. Your RA probably doesn't mind picking them up, but if you want to have lots of bins all over the place, you can pick them up yourself (MIT Medical, second floor, on your right from the staircase, follow the signs down the hall).

ps - the MIT supplied condoms are very good quality in terms of protection, and decent variety (colors, textures, etc.). this is the tip of the iceberg, in terms of overall variety. if you're picky enough to say that you don't like any of them, shop for yourself - there's plenty to be bought online, if you don't want to go to the store...