I bought one sealed mystery pack that I thought was fake. The sealing was done OVER the price tag and diagonal, which I thought was VERY strange. However, I am 99% sure the pins were real when comparing them to the real colors, weights, etc. of the real versions.
HOWEVER, many of the packaged booster sets are fake (the ones that come in the clear overwrap). I bought some at auction from one seller that turned out to be real. I then later bought more from the SAME seller, and they were definitely fake. So you can't even trust you will get the same thing from the same seller again.
So, regarding Ebay, I will no longer be purchasing the clear overwrap booster sets, and would warn against them, but I will probably try a sealed booster pack again.
I don't know about anyone else, but a lot of there cover pictures look strange to me. though. Like the bag is deflated?