I am one of those people that wished there were less auction sites, not more. As a seller, faced with hundreds of sites to proffer my wares, I am highly confused. I usually just look on ebay for all. If I ever stray away from that, then I run across hundreds of other auctions but many of these are just front pages that lead back to ebay.
Even if I find a site that is notebay then I still have a dilemma. Bidding for an item both on ebay and on notebay, how am I to know that the items are not actually one and the same item from exactly the same one seller who is going to take the best auction and close off the lower bidding, less-popular ones, without a sale? If I bid in both, effectively I am bidding against myself. I am also spending twice the amount of time for just one result on one item.
As a seller, faced with multiple places to sell my wares, do I offer it for sale in just one place and hope it has the widest audience, or would I be tempted to offer it in several (to try to capture a wider audience) and then blow out the lower bidding auctions? Again, this is a waste of the sellers time too. He is advertising it twice, just to sell one item.
Compare this to a real world example. In the UK, a popular Sunday morning exploit is to visit "car-boot sales". As it says, this is an event held in a shop car park before opening time, or in a sports field, or a school playground, or somesuch place. People turn up with a car load of old stuff that they want to sell on, pay the organiser of the event a couple of quid for a "pitch", and then sell the stuff they brought along, out of the back of the car, or off a small table brought with them. Some people sell now and again just to offload some surplus stuff, while others make a "pocket money" business out of it selling stuff every week, sometimes at multiple events.
Round here, on a Sunday morning, there are two or three events separated by quite a few miles. However, a few years back, there were a lot more. In fact, at one time, there was a big event in the morning, and then a mile away, another one in the afternoon. Guess what? 75% of the sellers at the morning event, went on to the afternoon event; and 75% of the buyers that were at the afternoon event had come along having been to the morning event first. So, in the afternoon, as a buyer, you had the strange scenario that the vast majority of what you were now looking at, you had already seen just a few hours ago, just a mile down the road. For the afternoon sellers, it was equally frustrating: most of their potential customers having seen the stuff in the morning and not bought it, didn't buy it in the afternoon either.
So, although at first the numbers of both buyers and sellers at the afternoon event were quite high, this quickly trailed off as the buyers weren't buying, and the sellers weren't selling. The lack of new unique content on the tables, and new customers (compared to the morning) to sell to, meant that the afternoon event folded and closed after just a few months.
It wasn't that it was a poor event, but simply that having two sales on the same day in close proximity meant that the latter one was a waste of both the sellers time, and the buyers time.
Can you see why I feel the same way about having less, rather than more, auction sites too? It is the same sort of problem.