Over and beyond what is stated above, GET PROTECTION FOR YOUR COMPUTER! One problem from signing on to reward sites is the spywares you'll get. They not only track down where you've been but in some cases download commands to change your settings too! Ad-Aware is free for personal use and a popular one.
In all honesty, unless I know I am getting a reward mailed out for sure, I NEVER use my real residential address. And more serious to me yet, I never print my real phone number. As far as I am concerned, unless they give me something I wanted, they shouldn't locate me.
The test drives are an easy and useful way to accumulate rewards. My Points has always been honest in resolving issues and crediting points in my experience. Blink is a site many use but I would not recommend because of their unpredictability and I have yet to see my points awarded from purchases made in the beginning of the year! The smaller rewards sites limit rewards absurdly unless you sign up for offers through their portals. Most of them are credit card offers. Do not go crazy applying for numerous ones for the equivalent of $10 - $15 bucks, your credit report may not look so good after that.
They award such low points that if you don't have at least a year to accumulate rewards you may not get anything out of them. In fact, you save more saving $0.50 - $0.75 a day staying away from vending machines than exposing yourself to online rewards programs.
Sometimes you earn a lot in purchases awarding double points, most times you do best in promos awarding 1,000 at one single time. Do your research and choose what is best to your situation.
I am a strong advocate of My Points and absolutely love their customer service.