> One tricky thing, though. The few times I saw someone trying to implement the task count, it would sometimes be the case the count couldn't be determined beforehand! So I'd see progress reports like: 1/123 done.... 42/124 done... 45/2616 done... 68/98213 done...

SharePoint search does something similar! It doesn't search everything, so it just says "about X items found" based on an estimate. Everytime you click on the next search page, that number gets a little more accurate