Don't underestimate the power of one person with a passion and determination.
I think plentyoffish got some good press early on and that got it the momentum. Plentyoffish is the only free dating site I've heard of, so there's a big reason to go there instead of other free dating sites.
The site design is actually pretty good IMHO, and sort of suggests that you're going to quickly get what you want to see and not a ton of flashy useless stuff.
I believe the incarnation came from something along the lines of "I wanted to learn ASP, so I made a dating site". Not sure where that plots on the graph of passion and determination.
I think plentyoffish got some good press early on and that got it the momentum. Plentyoffish is the only free dating site I've heard of, so there's a big reason to go there instead of other free dating sites.
The site design is actually pretty good IMHO, and sort of suggests that you're going to quickly get what you want to see and not a ton of flashy useless stuff.