I googled it. It doesn't exist. And now it's mine. Here's my stab at an Oxford's definition, if I can get this thing to catch on.
1. Complete or partial loss of memory of website login username and password information. 2. Having a large number of unrelated usernames and passwords such that an individual becomes incapable of remembering them. 3. An independent virtual state consisting primarily of internet-related detritus, files or data recorded or written in versions of software no longer in common use, and multiple digital photographs that are not intended for print. (see 'Photoblivion')
That's mine too.