Why do you all think it's spam?
I have 17k items in my inbox and most (99%+) of it is legit. We have very effective spam filtering in our office, so I don't get a lot of crap.
My inbox serves as a communications tracking system. Pair that with X1 or Google desktop search and I can bring up emails on any subject that I have corresponded with people on in seconds. The fact that I use those tools, rather than move things to folders is a choice I've made. However, I do need to archive some of this stuff