I think Dave's comments about HaT and such, are accurate and pretty much mirror the overall sentiment and observations noted here.
As eBay Motors (and eBay itself for the most part) pretty much has, HaT has and will increasingly become the domain of corporate entities and flipper/dealers and auction companies, and the "enthusiast" component selling interesting cars on HaT will continue to become less and less. And this opens up opportunities for other sites perhaps like MBMarket, PCarMarket, etc. for "the rest of us."
HaT chose to follow the money, and strayed long long ago from its enthusiast roots. Nothing wrong with that....it's America !! No question that the car auction company scene and associated auction web sites will continue to consolidate in the future. Look at the recent news about Gooding & Company!
It's going to be interesting to see what entities continue to fill the gap - both established sites and I'm sure new ones that will crop up. Likely we will see business models and innovations in the coming years that we've never seen before.