There may not be two types of people in the world but there are most certainly two types of people on the dating site okcupid.com--those who think WAY too much about online dating and those who just want to online date for free.
The site has full functionality for free, though you can upgrade inexpensively for a few perks. Being free has given it a rather large user base. This can be a problem for a dating site, as a key component consumers look for in a dating site is sorting away undesirables.
Okcupid (or okc as its affectionately known to many users) overcomes this by doing lots and lots (and lots) of sorting. The thing to understand about OKC is that it's actually an outgrowth of the old spark.com. In the late '90's, Spark.com was a place to go for used college term papers and inventive social experiments, like trying to make cheap vodka taste better by repeatedly filtering it at home.
One such experiment was a dating algorythm. Soon, the dating algorythm had its own site and was making more money than its predecessor and they ditched spark.com, which ironically enough is now a more run of the mill dating site. OKC still maintains that inquisitve nature and its users reflect this--they tend toward the cerebral.
In using the site, you answer lots of questions and surveys and tests, to the point where some people are just there to waste away their days taking fun little tests like what type of musical instrument represents your persona. In the end, this makes it a fun site--I've met lots of people from it over the years, including my current girlfriend--but it does require a little bit of your own sorting to find the people who are actually there for dating.