I've been using Crowdtap for several years now. I fill out surveys and they send me gift cards; my favorites are Uber and Burger King, but they offer lots more. I've never had any problem with them. You won't get rich but it's really nice to earn $5 or $10 here and there for surveys that are easy to fill out (and sometimes kind of interesting). If a friend asked me to recommend survey sites, Crowdtap would be in the top 3.