The tag mass-assignment has been included in http://meta.stackexchange.com/questions/128315/the-great-stack-overflow-tag-question-cleanup-of-2012, with the comment
(not sure about this one, it seems strange and has a smell, please provide input)
Input was provided. Of course, since this was the 68th answer, it didn't receive much attention.
The tag wiki has no reservation anyway.
DO NOT USE - Removed as part of "The great Stack Overflow tag/question cleanup of 2012" - See link in Tag Wiki for more information.
A simple google search shows that this is a well-known programming concept, at least in the Ruby on Rails community; a perfectly cromulent tag. Please remove this tag from the cleanup list.
(I tried proposing a tag wiki. I'm not a RoR programmer nor more generally a web programmer, so if you're familiar with the concept, please improve.)