Well buying memory sticks anywhere but a trusted store or source is a gamble. Most of the time they will not work, but if you buy from an honest person they may. Selling fake sticks is a big money-maker for people because they sell for high prices, so what would stop them from scamming people? Buy from a EBGames or GameStop, a trusted place. Which would you rather have:
a) paying a bit more for a good-quality , working memory stick
b) paying a cheap price and wasting money on something that doesnt work