Basically, nearly all of MS Pro Duos on ebay are bulk/fake. Basically bulk and fake aren't worth distinguishing because they both fail. Easiest way to check is put it in your PSP, boot up, browse XMB and locate MS, press triangle (IIRC) and "Information" and next to MagicGate it would either say enabled or a dash (" - ") meaning disabled. Only genuine MS have MagicGate enabled, I haven't seen any fake one that has.
Fake MS is hard to distinguish when you run a speed test on it, it's average speed is almost the same as genuine (some really crap junk don't even get half the genuine speed) but it gets horrible spikes, and when that happens while you're running something on PSP, you either get a serious slowdown (for example mp3 is not playable due to too much popping/noise/etc) or frequently freeze.
You can try Ebay's "Item not as described" claim especially if the seller posted Sony's picture instead of his own shot, for Sony's picture is Sony's genuine MS and what he sold is not, it should fall under "Item not as described".
I got mine bundled with my PSP, so obviously fake, also came with fake Hori screen protector (works fine though, no sticky mess)
And yes, there are also people who sell fake TF, if they can sell a fake TF for $2, they'll do it because they still make money. Depends on where you live, but one time I spent what's equivalent to US$4 on a restaurant and so many people were staring at me because nobody spends THAT much money for dinner for TWO.
I'd suggest 4GB Sandisk over Sony, and for Micro SD's concerned 2GB models should be about the same, it's only the 1GB MIJ Kingston that kicks ass, don't think 2GB does.