Something that makes me insane, and it happens a lot, is when an ebay seller creates multiple auctions of very similar products that all end at the same time.
Not all of us have unlimited funds, so, just for example, if there are 3 Northgates that might go for $100, ending within seconds or minutes of each other, (at a time when we cannot be certain of sitting directly in front of the computer with a solid internet connection) and if a buyer had $100 to spend, he could only bid the $100 on one of the 3.
If there was, say, at least an hour between them, then he could juggle his bids and perhaps get the 2nd or 3rd one at his max price even if he missed the first one.
Realistically, if he was constrained by the $100 limit, he could only bid $33 on each, or $50 on the first and $25 on the next 2, etc.
In any case, both buyer and seller are punished in this scenario, because the seller is short-circuiting the process that might yield him the best return, and the secondary buyers are simply flapping in the winds of chance.
Likely, some buyer or buyers will get a bargain in some of the latter sales, as the herd of potential buyers is thinned out, so there is an upside for somebody.
I strongly recommend putting at least an hour, and, preferably, a day between end times of similar items, for the best and most consistent returns.
Just my opinion, of course.