an alert on its website telling buyers how not to be fooled by fake clubs. "To protect our valued customers from fraud," it begins, "Callaway golf shares the following warning."It goes on to say that consumers around the world have been duped into purchasing "so-called brand-new, authentic Callaway Golf products at very low prices" on Internet auction and retail sites "that have turned out to actually be low quality fakes." Such fakes, says Callaway, have dramatically increased over the last few years. When a single driver can cost $450 at retail, falling prey to fakes can get expensive.How do you spot counterfeit clubs? Callaway's website provides some guidelines.