Just being devil's advocate here, because I think the No Overwrite extension is great, but in the cases when you see your name somewhere and it's wrong, it's irritating if you can't fix it. It may be a typo, or your first and/or last name may have changed due to one of a whole variety of life events that could have happened since the information was entered.
The alternative to allowing people to fix their names is to require a call or email to the office--staff time that costs nonprofits money.
Also, although I'm quite aware that many people ignore all this, it takes a certain amount of bravado to go on a form, blow past the warning box which offers to give you a blank form, and pro-actively replace a series of pre-populated fields.
Most individuals would never think of doing such a thing, and many charities have never had a problem like this. On the other hand, it seems to be par for the course for trade association members. That CiviCRM allows for either option (flexibility by default, or structure via Xavier's extension) is a real benefit.