Related to It should be possible to retag a question without bumping it to the front page but different because that question asks about editing existing tags for consistency, while I also care about adding tags to questions or removing poorly chosen tags, particularly in the context of SE2.0 sites, not solvable with moderator mass tag merging.
I do a lot of retagging on the math.stackexchange SE2.0 site, so I've noticed that when a lot of questions have had their tags modified, they get bumped to the front page as 'recently modified' even though none of the substance of the questions or answers have been changed.
This is particularly troublesome early in the site's life since new questions do not get asked quickly enough to mitigate the problem, and any users can create new tags, so many extraneous/useless tags get created. Since tags are so fluid early on, there is a lot of reliance on users to make sure correct tagging is maintained, especially since we don't even have site-specific moderators yet!
Edit: Chacha102's answer describing why retags should be visible is a good one. I suppose the request is not that retagged questions should be hidden entirely, but that the default behavior of the "active" questions should be to show only substantive changes, with the list including modified tags as a separate sort method or user option.