A very high percentage never change their auto-generated names (the first two letters of their last name, plus 6 random numbers).
I once sent an e-mail to those people reminding them of how easy it is to change their ID (and giving them a link to the change page) but very few did, so I gave up.
It is especially frustrating because a huge percentage of the people who can't remember their ID and need to have it e-mailed to them (and they rarely can figure out how to do that themselves) are people with the auto-generated IDs (I suspect they are not very computer savvy).
Remember that all of you can change your ID as often as you like (especially if you suspect someone is targeting you), but very few people do that either.
Bruce