Yosemite does not like emptying the trash

I am on Yosemite (10.10.1) and I noticed the annoying habit of not wanting to empty the trash -- it keeps whining that The operation can’t be completed because the item “whatever” is in use. This is starting to piss me off - I can go to .Trash and remove stuff by hand, but is going on? Once a file is not in use and has been binned, why can't the OS recognise it's not actually linked to any application? This problem has come up whether the app used for that kind of file is still open or not btw.