You might think that counterfeits exist only in the realm of "Mark Jacobs" and "Guchi" purses, but there are fake and black-market beauty goods, too. I love a bargain, so I wind up buying a lot of housewares and accessories on eBay. But when it comes to shopping for cosmetics, you've got to be careful. I've found quite a few counterfeit eye shadows, lipsticks, glosses and fragrances—all offered at prices that are too good to be true. While there are honest sellers out there, a few folks are out to make a quick buck.

Why is buying counterfeit merchandise a bad idea? There are a few reasons, but first and foremost is your health. If you don't know where a product really comes from, or what ingredients are inside, why would you let it touch your skin? Counterfeits also funnel money into shady operations, and—oh yeah—they're illegal. And on a less sinister level, the colors just aren't accurate!

To find out how to avoid buying fakes, read more

Common sense will take you a long way. If a deal seems too good to be true, it probably is! For instance, the 12 "MAC" eye shadows shown here were being auctioned on eBay for $24.99. Hmm, that's a pretty low price, considering a single shadow is $14.50 in the stores. Now, I can't tell whether those eye shadows are genuine or fake, but the price seems a little odd.

For that particular auction, I also looked at the seller's feedback, which had complaints by bidders who claimed the MAC shadows were fakes. The seller also had dozens of similar auctions; why would one person have literally hundreds of "new-in-box" eye shadows? Is there a possibility that this particular seller is legitimate and just being accused of selling fakes? Of course. But it's not a chance I want to take.

For most people, common sense will help you spot obvious fakes, but the counterfeiters are getting better and better at making their junk look like the real thing. This detailed guide has great examples of counterfeits lined up to the real thing, and I recommend it as an excellent reference.

What do you think? Would you buy counterfeit makeup to save a few bucks, or would you rather save up for the real thing?