I am currently putting together a project, basically a homebrew 8088 computer, and eBay is virtually the only source for parts. I have noticed a few things that would apply to buying pretty much any component from eBay, although I am talking about older parts here.
The first thing is knowing your part number. D8088 or D8086 is a ceramic package, yet probably half the items claiming those numbers are PDIP. This applies to pretty much any chip from the era. While there should be nothing wrong with plastic packages, that is legitimate, it should have a P prefix. In this case "vintage" and "collectable" are thrown about freely with no regard to what is actually being sold. Even if the parts are legitimate, they are being offered for a huge premium. To be fair, some sellers do mention they are selling clones. I would be more inclined to buy from them than the BSers. One thing I find interesting is the mythical 8088-1. You can find fan sites that list it, without any image. While the 8086 datasheet clearly states an 8086-1 version, the 8088 datasheet only mentions the 8088 and 8088-2 as the only versions.
Those are the two main things I have run across so far, I am sure there are others. Please do not attack China on these discrepancies, they come from sellers all over the world.
Anyway, just voicing some of my frustrations from looking for sources to parts over the last couple days.