I think it would be preferable to keep a log of bulk edits that were performed in a global(?) history, and allow them to be reverted easily? I think that would mitigate the issue described in the comment above, and provide value in the event someone unintentionally bulk edits the incorrect set of tasks / objects.

One specific thing we're starting to see more of is test users signing up and bulk-associating or bulk-merging large numbers of tasks. There doesn't seem to be any specific intent behind this, but I think these UIs are shiny and make it easy to click a lot of buttons and have a large effect. Here's one such user on this install, who has registered three accounts just because they like clicking buttons so much: