I have a pretty close friend who got a 42 inch LG high def TV for completing 30 offers, he canceled them all and ended up getting it for like 70 bucks... Some might be worth it...
About 3 years ago, there were a few legit sites. It was A LOT of work, but I got a 20" Sony LCD Monitor, a PSP (when they first came out), a iPod shuffle, and a Mac Mini. But with all the hassle, If I had to do it over again, I'd buy it if I really wanted it.
In '05 I got a Mac Mini, Nintendo DS, iPod, iPod nano, and a 19" flat screen monitor from one of those sites. Free? No. But a whole lot cheaper than from the store. I did the DS first and then I got addicted. I even found a message board that was equipped for trading (I'll sign up for your if you sign up for mine)!
But now this particular site has made it more difficult because they only give you 90 days to get all your sign-ups. It took like a year to get all 10 sign-ups for the Mac Mini.
All that referral crap surely can't work. The only thing I got free was a PS3 with my phone contract...that was pretty sweet...man i love nullsoft medialink!