You're not going to make quick cash filling out surveys. That's the bottom line.
And if you give your email address to the wrong survey site, you'll be flooded with tons of spam. Having to pick through pages of spam to find your real email gets old REAL fast, trust me.
That said, some surveys are actual scams, whereas some are up front about what you have to do and what you'll earn. Usually, what you'll earn are coupons, "prizes" of dubious value, gift certificates, etc. But not cash.
So if you enjoy filling out surveys and would like to earn points toward prizes, then by all means, go for it!
If you're interested in doing surveys for cash, I'd suggest looking into a local marketing or product testing firm. There are legitimate companies out there that will pay you and your friends to try new products like deodorant, shaving products, toothpaste, etc. Normally, you do have to go to the company and try the products there, so they can observe and ask you questions; but they pay quite well, too.
So check your local yellow pages and ask around. You can get paid for trying products, but it's probably not going to happen online.