John once said he believed the generic covers were a way of covering the asses of late artists--who knew when the books would hit the stands, so who knew what to put on them?

One theory I have (especially with Ultimate Spider-Man, the worst offender of this kind of thing) is that, with every cover looking EXACTLY the same as the last (and the next), the companies hope fans will buy the same book twice by accident. As in, "Do I have this issue yet? Better grab another copy just in case."

Yeah, since the covers of so many books are so generic, It's hard to keep track of which issues one has.

As opposed to memorable stories having memorable covers.

I agree with both those points, Chris. I was overjoyed to see the dialogue on those 2 Superman covers.

 The Detective covers are disappointing me greatly. While I'm enjoying the stories, I'm seeing each month's cover in the shop and am unable to tell if I've read it. That's the worst thing a cover can do..be so generic that each month blends together. 

I agree that the covers to Ultimate Spider-Man can make it difficult to tell if you've bought the issue before, but it definitely doesn't meet the first argument.  Throughout it's run the book has shipped 12-18 issues a year and hasn't been late once over it's 100+ issue run.