Yes, I tried that when I was acting professionally and it doesn't ever really pan out. At least that was my experience. Most sites do one of 2 things. 1. You sign up and then they tell you there is a monthly membership fee for the right to be considered to take their surveys and won't guarantee that you even make your membership fee back. or 2. The compensation is in the form of either sweepstakes entries or points to redeem from their catalogue of useless crap. I do 2 that fall in the latter category just for fun. The catalogue has allowed me to give several extra X-mas gifts for nothing but it's mostly magazine subscriptions, travel mugs, posters and stuff.

There are some transcription agencies that I did some genuine work with but you never know when they're going to call with a job and you will end up working long hours to meet each deadline.

Hope that helps.