The through hole stuff hasn't been bad for me, as far as resistors. Caps on the other hand.
Resistors, SMD or Through Hole, and LED's are probably the only electronic component I will buy from Ebay now. Even then, sometimes buying SMD components in bulk (like 5or 10k worth at a time) is still cheaper from the big name distributors than eBay.
I have bought IC's, SMD and through hole, in the past from eBay, and I will NOT do it again. A fail rate of about 50%, and the ones that didn't fail weren't up to specs. Sometimes you'll get lucky and the chips are genuine that just get rejected from an SMD assembling machine and there's nothing wrong with them. It takes more time to sort through the reject bin of these machines, place them back into reels, and reuse again, than it does to just throw them out.
But, you have no way of knowing if you are getting these parts or fakes, until you get them. If you ask them, they will say, 'oh, yes, our part come from original manufacture, you can have confidence in us'. Don;t trust them, they are 90% of the time fakes and are just crap.
Some stuff, like National Semiconductor parts are/could be completely legit and are just new old stock. Since Texas Instruments have bought out National Semiconductor some time ago, all those chips have been rebranded with the Texas Instrument name. In fact, for example, the LM2596 voltage regulator chip of both the Texas Instrument and the National Semiconductor, the Data sheets are identical, except for the manufacture name. In fact, both data sheets still look like scanned copies from the 70's. So these parts could just be old stock that assembly manufactures and TI themselves have just sold off cheap to make room for the new branded TI chips, and then in return get sold on eBay.
As it has been said before on this Forum, for the most part, if the person you are buying from has an eBay store that only sells electronic components, you have a better chance of getting original manufacture parts. But if you buy from a person that also sells women's designer (although probably fake as well) Bras and Panty's, then you have a 99% chance of receiving FAKE electronic components.
Just to clear up any confusion, I don't shop for Bra's and Panty's on eBay. I goto Victoria's Secret. Better girls too look at there.