I know plenty of people that have got dates thanks to Zoosk in the last few years.
By definition most people wouldn't have heard of internet companies that are not among the 20 most trafficked sites even though they might be serving a pretty large market with tens of millions of users.
Companies in the dating market solve a very real need and the marketplace is still very nascent and far away from saturation. I definitely expect that we will have an internet dating company with Market Cap > $10B over the next 5-10 years.