Earlier this year, Christian Louboutin launched an operation to strike a blow to the counterfeit business.
It was a great day for all Louboutin lovers. eBay, at one point inundated with fakes, is now nearly clean. It's quite a feat. At some point there were more fake Louboutins on eBay than there were authentic shoes. One had to wade through pages and pages of counterfeit crap. New fakes get listed daily, that has not changed, but the time in which they are taken down and the number listed has improved considerably. The fakes still look awful and obvious to a trained eye; that has not changed!
When in doubt - check with the experts at the Purse Forum. There is always a thread there for authentication. The ladies at PF are not professional authenticators, but they do have bucketloads of experience with Louboutins. To be completely safe, however, shop only at authorised dealers - you can find a list of them on christianlouboutin.com.
Remember, some consignment stores have been discovered to carry counterfeits. Names will not be named; just be careful. The store may, or may not be aware that their Loubies are made in China instead of Italy.
A great number of sites selling fake Louboutins still remain. Just google "Louboutin" and you will get pages and pages of fakes. You don't want to give the sellers pageviews or ad revenue, so don't click on any of the results.
Stop Fake - Christian Louboutin has a very long list of fakes websites that they have identified. The list is viewable here.
Here is a list of actions they have taken.
You can email them if you find a site which sells fakes. Their email address is on the bottom of the main page.
Please note that I am not affiliated with Christian Louboutin - I'm simply crazy about his shoes.