The reason for the Junk folder (if you're interested) is because sometimes you actually *sign up* for a mass mailing list (like I just did for the band They Might Be Giants), or a mass email from a friend (for something like a birthday party) who doesn't normally mass-email, or a dozen other exceptions that look to a computer like junk mail but are in fact something you want. Apple's junk mail filter (with a little training from you) is actually pretty remarkable in its ability to put junk mail in it place (which then periodically gets deleted).
The problem is that most people don't "train" the filter, or don't do it for long enough (about a week is good), then complain its not accurate or doesn't do anything. It actually works great if you set it up and use it as directed.
(I do agree that ISPs should do more to handle spam on their end, however, but have always found it ironic that Google -- the company that scans your email and uses the results to spam you on the web and sells your info to other advertisers -- has itself a very strong provider-level spam filter. Little bit of a common kitchen cooking component calling a water-boiling device a racial slur, seems to me ...)
I am going to get that straightaway 
