About a year ago Facebook changed how email addresses show up. The default now is your.facebook.username@facebook.com:

This wouldn't be so bad if email people sent to you@facebook.com actually reached you, but their spam filter is very aggressive. So aggressive that, unless the person sending the email is already your 'friend' and sends it from an address registered with Facebook, the message will go into your 'other' folder and you won't even get a notification. Until I realized it did this I thought people who I wrote to were being kind of strange in not replying.

Update 2013-06-10: Daniel points out in the comments that he hasn't had a message go into "Other" in a long time, and checking now I haven't either. Facebook may have fixed their filtering. It would be helpful if you sent a message to jefftk@facebook.com and then wrote jeff@jefftk.com to ask if I received it.

When I want to send friends emails I look up their address on facebook, and it's surprising the fraction of time I see @facebook.com email addresses. If you want to get email from people you should check your info and make sure the visibility settings on your real email address are as you want them.