A recent post by Anil Dash is worth reading and goes over the use of “toread” as a tag:

via Christina’s LIS Rant I found that there is now a paper about the use of tags as emotional or task related (pdf) instead of actually about the work. These are tags such as toread, toblog, fun, etc.

I’m guilty of using toread and toblog more then I should as it is unlikely I’ll actually get back to the items. Maybe I should just use bitrot or blackhole instead. Some of the tags are useful and interesting to wade through, though. Looking at LibraryThing’s list for must read, favorite and recommended probably tells you more about the items then just ratings alone. There’s obviously less data but even AADL’s SOPAC has tags like BestOfMine and to read.

While not directly related to the content of the item in the way traditional classification would be, it adds a level of information about the work you might not get otherwise. Finding a book about economics that’s fun to read is a little easier with more emotional tags.