Does it really matter if they're bootlegged if they look nice?
Well, It matters to me because I thought they were the real thing. Sure, I love my Marisa and Reimu, and will not get rid of them because I found out they were bootlegs.
Bootlegs, even if they look good, hurt the company that first made them. ZUN gets nothing from me buying a Bootleg. Now, I am not sure if they guy selling knew it was a bootleg or anything. He didn't even know who the characters were I think, and only had a few, so I bet he got it as a deal, and he was the one that got scammed by the bootlegger.
Bootlegging is a practice that must not be supported in any way. Buyers buy products under the assumption that they are made by a certain manufacturer, which they aren't, which not only attributes possible (and likely) design- and material flaws to the supposed manufacturer, but also decreases the item's value should the buyer ever decide to sell them again. It's disrespectful towards both the buyer as well as the original manufacturer. Of course, it depends on your moral code, but to me it matters a lot.
Speaking of which, I don't think I could ever buy something at a convention, unless it happens to be the booth of a shop I frequent. Way too many bootlegs around.
It matters a lot too, but one must take into account that sometimes the sellers at these cons may not know they are selling bootlegs. Some of them don't know all the characters they sell, and get them from Japanese sources. Those people may be the ones selling them bootlegs, and the people at the cons may think they are real.
As for shopping at cons... I just enjoy it too much not to do it because of a fear of bootlegs. Sometimes you can find really rare stuff that you can't find online anymore. Plus with a little research, you could tell if something is bootlegged. Like I asked about those Nendroids I bought, and got answers quick here. The con I am going to tommorow has that store there as well, and I may pick up the Sanae one, since I heard she is rare, and 70 bucks for her is a steal.