I had a look at other threads and couldn't find the answer. Since MobileMe has junk mail filtering - does that mean MobileMe on the iPhone will have a junk mail folder? Not having to wade through hundreds of junk email would sell me MobileMe.
If you set up the junk filtering in the web interface then it should filter before pushing to the iPhone, but if you just set it up in the OS X Mail app then you will not have filtering on the iPhone.