As a user, I prefer when a service uses email for usernames. One reason is that I can remember my email address, even if I don't use it. Often I forget the usernames that I use to sign up for various services. The other reason is that I know my email address is going to be unique, so that saves me from playing the "username is already taken" game.
I don't really have a problem with spam or known email users who are over active. Gmail does a pretty damn good job of filtering the spam. Custom filters do a good job of clearing things that aren't really spam but still annoying.
- drawbacks
- spam
- they change
- they get hacked, which in turn means your accounts have been hacked
- advantages
- easy to remember
- immediate conduit to your user
- automatic recovery built in (see drawbacks)
- built in verification of identity (somewhat) of user
It's a tough choice. We used to use email addresses but of late we have switched to simply allowing people to pick a unique nickname.The deciding factor was the fact that more and more people perceive giving their email address to a service as a serious barrier to participation.
My solution to many of the general set of problems with email you cite was to get a Fastmail account (https://www.fastmail.fm), which does a fantastic job of spam filtering and would allow you to filter the email from those pesky relatives.
And as gexla notes, you must have a working email address to do a whole bunch of things on the net.
But you're not required to care.