This would be so much easier than adding new tags to distinguish them. I could also make sharing tasks easier -- just share out all tasks in a project to the same set of users. Reporting, likewise, could see some simplification with the addition of project-based organization.

Sometimes when I'm in then middle of a task I get a phone call which I time as well. After this phone call I would like to be able to pick one of the previous tasks and continue that one without having to enter the tag and the comment again.

I would like to be able to add a "Billed" tag to entries when I generate an invoice. This way I can run a report excluding all "Billed" entries to make sure I don't double bill someone.

I can think of other uses too but the example above solves two problems.