I wrote firstname.lastname@example.org to complain about their concept of a valid e-mail address a while back, when I needed an account for a product at work. The result was less than stellar. Facebook.com has their own idea at what constitutes a "valid e-mail address" which excludes a large portion of the e-mail address space, but should work with the e-mail address that most universities will hand you. Still, this gives a very unfriendly view of the company, and helps support the view that Facebook.com targets the technologically illiterate.
Do you stay awake at night, thinking of the things you should worry about?