As I have mentioned before, it seems to be increasingly common to experience IC supply problems, with long lead times becoming depressingly common. For example, I have three Analog Devices parts sat in my shopping cart with waiting times of 10, 11 and 15 weeks! This means that no matter how well meaning we are, it is massively tempting to look at the "grey" markets. Yeah, you know what that means. The risk of cheap, out of spec, and often totally unrelated components getting re-printed with the markings of much more expensive devices.
One example is the classic OPA627 op-amp much beloved of serious audiophiles around the world. This amp is expensive at the best of times, but last year the manufacturer and all the usual distributor stocks were empty. Conveniently, most op-amps have exactly the same pin-out and, unless you have the right test equipment, they are very difficult to tell apart. Search Ebay for them and see what a wide range of prices you get. Then consider that even in 1000+ quantity, TI prices them at $12:25.
Anyway, if you are contemplating sourcing from anything except the big distros, I would advise you read this article on counterfeit IC detection: http://www.aeri.com/detection-of-counterfeit.asp