NONE of them? I assume that means you've reviewed the more than 4000 that were submitted? I hate to immediately jump on the defensive, but I was a little put-off by the statement. I've used the site for a logo design that I was quite happy with and I've also submitted a few designs that no one was happy with (and for good reason, I'm a terrible designer). So while I have little experience with it, I do think it's a good resource and shouldn't be denounced so quickly.
I've never owned a company and certainly have no real basis for this assumption, but still I assume that I would much rather have thousands of designers at my disposal willing to do iteration after iteration in order win a "prize" and some notoriety to do branding for my company than a single firm who I would feel like I was stuck with after any amount of investment.
Now while I will submit that something of this nature will certainly bring out those "trolling for prize money", I don't agree with the mild implication that the format of the site has nothing more to offer isn't a fair assessment.