Being able to see a person serves purposes other than finding out how attractive they are. Trust (or rather, feeling like you can trust someone) is another one. I used a roommate search site once, and noticed I usually had a much better gut feeling about people who included a photo on their profile than people who did not. (Something similar happened for people who used their real name (or something that sounded like a real name) as their user name, even if it was their first name only.)

I wonder how the profile format of online dating affects peoples' interactions and choices. I just now realized how similar the format is to online shopping. That's a bit creepy, actually. Some form of simulated speed dating seems like the obvious alternative. People who become friends online tend to meet by making posts about the same topic on various types of social sites. I'm not sure how that could be adapted to use for dating.

In person, people usually start with small talk when they meet for the first time. I wonder if it's about comfort level - talking about inconsequential things lets people establish some slight trust so that they can talk about topics they really care about later. If so, it might be difficult to make online dating deep. I notice that at least some young people have few inhibitions about telling personal things about themselves online, though, so maybe anonymity could actually help in this respect?