Well, to me, all apply!
A) - why I own an early Rega Planar 3, an Aura amp, and Pioneer PD-S904 CD player - items I coveted at some point in the past, and why I have a hankering for some TDL speakers...
B) - If you don't do your research, very easy to get carried away with what seems to be fetching money at the moment - a lot of crap is "bigged up" by the seller - in a way, the 70's Sony amp I bought was a victim of this - I only really wanted it as a collectible piece (OK, for the big VU meters!) but it doesn't sound brilliant compared to a modern amp - also makes me laugh how you only ever see an ebay ad saying how fantastic the piece of kit sounds - in which case, why are you selling it?!
C) I agree - a classic should have something of "merit" but that can be a very loose term - it could be that it was the component that defined a generation and was good but is not particularly rare (say an SME 3009) or its merits might be that it is rare as hen's teeth, yet still not sound that good... Or it could be that it is a design classic, but fragile as hell - lots of comparisons to the classic car world, I think - no one would doubt that many Alfas and Lancias are classics, despite the fact that they rot at the first sign of H20 and fall to pieces if you actually use them!