freitasm:I trust only cards bought from Amazon, when they are sold and shipped from Amazon. Anything else and you risk getting 1GB cards that misrepresent to be higher capacity.
Even direct-from-Amazon isn't a guarantee, you can get fake stuff from third-party sellers there. What I do is go to the manufacturer site and buy from their approved local reseller, e.g. for Sandisk they link to Ascent (which is a good place to buy stuff anyway), so I just ordered from there.