What's so wrong with secure Email?

Secure email is a ridiculously simple concept, but unfortunately with very few simple to use applications available to the public.  MailPile is a startup who is attempting to come up with a good working solution.  They also have gotten quite a bit of public backing (they raised $135k with a goal of $100k). Unfortunately, as Slashdot points out (and ArsTechnica), PayPal seems to have unfairly frozen their account to apparently prevent them from making easy to encrypt emails.