I've done a fair bit of online dating in my day. Heck, my dad even suggested it to me after I met (and sometimes dated) a fair number of "real life" duds. It's much less random than bumping into someone on the street, and it's easy to vett out the guys who obviously aren't compatible with you.
Online dating has worked well for me; I met my current boyfriend online. So it was with great interest that I read a story in this week's NYTimes about the science of online dating. In the article, the author discusses eharmony, match.com, plentyofffish, and several other for-pay dating sites. I like her conclusion -- that no one site is better than another -- but I think she had some major oversites in her article.
For starters, she only discusses sites that cost money. Yes, there is a big segment of the online dating world that is costly. But there are also sites that provide the same services for free. I suppose I'm biased, since I've never paid to use a dating site. However, I have watched other friends pay for their subscriptions, and I really don't think my experience was that different from theirs.
The two sites I've used predominantly are craigslist (CL in net speak) and OKCupid. CL is substantially different from other dating sites, as users just post a brief ad and sometimes a picture, but it is one way to meet people. I've dating a handful of fellas from CL with the net gain of one short relationship. OKCupid is much more like match.com and other sites; you post pictures, a profile, and some stats. You also answer a lot of questions about yourself. The nice thing about OKCupid is that you can always answer more questions, at your own pace, to help increase your chances of matching well. No one sees the answer to your questions, but the computer uses your answers (which include your answer, your desired answer in a mate, and how much you care about the question) to match you up with others.
OKCupid has done me well. That's where I met Matt, and I also had another boyfriend from the site. Better yet, I gained several friends from the site, and I think that's the true benefit of a for-free dating site that offers lots of options (you can look for just friends, a hookup, casual dating, or serious dating). I wouldn't say the process is substantially different, but the benefits of not having to pay can't be overestimated. Plus, knowing the service is free helps take the sting off of the multitude of crappy dates (ratio? probably 2-3 crappy dates to each decent guy that I met).
In the end, it seems to me that what matters most is adding to your repertoire of how to meet people. With online dating, I had another tool in my kit that helped me socially engage with the people in my area. And as a young adult who no longer has the social structure of school to help me meet people, I appreciate every method at my disposal for social interaction.