Recruiting Laboratory Participants

I am in the process of revamping the Internet laboratory, as I'm trying to increase the number of participants. Some very successful websites recruit ~500/day. I have been averaging about 30/day -- still respectable, but it limits what I can do.

In this context, I read recent reports from the folks behind Phrase Detectives with interest. Phrase Detectives, it appears, gets a slightly greater amount of traffic than I do. What I focused on was their method of advertising and how well it works. They noted that their traffic comes in the following forms:

direct: 46%

website link: 29%

search: 12%

Facebook advertisement: 13%

Then they looked at the bounce rate (the number of visitors who arrive at the home page then scoot away) for each of these sources:

direct: 33%

link: 29%

search: 44%

Facebook advertisement: 90%

It appears that paid advertisements -- the only one of these sources that actually costs money -- isn't worth much. In the end, only 4% of visitors who didn't bounce came through the paid advertisement.