Staff will often have their name or some variant of their personal identity in their university email address. For me, it would either be z.whittaker or zack.whittaker, or z.a.whittaker, depending on the institution's policies.
Students on the other hand dominate the register of users so there are often more combination's of the same name, leading to alphanumerical addresses which include the initials of the student. Depending on how many same combination's of the same initials, an added incremental number will be added. For me, I have zaw2 which is my bog-standard university email address, and zaw3 as my overdraft account because my previous account exists.
Luckily I have a strange initials making my email address interesting to say on the phone.
Consider @mediaphyter. For those who know who @mediaphyter is on Twitter, you'll know her overall online identity as the mediaphyter. Jen Leggio uses this online handle and identifies her as who she is, as no doubt there are other people out there with the same birth name as her. It's not just a username - it's an online identity.
So if that identity is already established on the web - and considering the way the web is nowadays, you can find more out about someone on the web than anywhere else - why shouldn't universities embrace this as a wider form of identity branding?
Instead of it being her initials and an incremental number, why not firstname.lastname@example.org or email@example.com?
To me, that makes more sense. That is, unless two or more people have the same handle, and that's when you would throw them in a ring, and watch them wrestle to the death to (literally) claw their identity back.