Email addresses, agreed, not so much. But one thing that annoys me where I work is our logins are of the form 'u0123456' (roughly sequentially allocated, but starting from 0100000)... and they're tied to our source control system. So you look through the commit logs, and all you can see are Unumbers - no names. Half the whiteboards in the office are covered in lookup tables of U-to-name.

It's a real downer when someone joins the company too - pretty much the first thing you have tell them is "you're a number now - everything in the company is accessed by this number". You can see in their eyes an "oh shit what have I gotten into" moment.