This is not a new issue with Windows 7, it's identical to Vista. Even XP did it, though it gave you a little more info.
The Read-only attribute is a throwback to the glory days of DOS and the command line. Command line tools will still balk at overwriting files with the R attribute.
I guess they figure in Explorer that if you've okayed the operation then it should proceed.
However
, it would sure be nice if Windows would at least change the "Do you wish to overwrite" prompt wording when it's a Read Only file like XP did... XP told you that the file was read-only in the process of prompting you to overwrite it. Windows 7 / Vista do no such thing.
This is from XP:

This is what Windows 7 shows:

Looks like more information at first glance,
but is really less useful yet takes up more space. Note, for example, that the newer dialog doesn't bother to show the seconds in the file time or spell out the month.
-Noel