Global Test Market is a decent standard of what you're getting yourself involved in. Their practices are not any more or less shady or reputable than almost any online venue – survey or otherwise. Just like Facebook, when you identify yourself accurately with Global Test Market, you can expect them to use that information in any way possible to make a penny. The great news is they inform you and ask for consent first.
Valued Opinions – Decent site with reasonable surveys ($2 for a 20 min survey). Everyone is annoyed by this site because they tacked on a $2 few to the Amazon $20 gift card and $5 to the $20 Visa gift card so it costs $22 to get the $20 Amazon and $25 to get the $20 Visa. They claim its because of extra fees they incur. I dunno. Also, it can take weeks to get credited for a survey which is frustrating.
When companies want to better focus their marketing, advertising, and product development efforts, they will contract with a market research firm to target their ideal demographic (for example, men between the ages of 40-60 who play golf), and gather information about consumers’ opinions on their product or service. You can read this article, to learn more about market research.
Paid survey site companies invest billions of dollars into marketing research online. They always want to find out more intricate details of a consumer's relationship with their product. Whether it's a new television show or just an existing product line, companies like Disney, Samsung, and Sony go to great lengths to find out their ideal audiences.