Yea, I used to think show people kept their dogs thin so they would not go over 7 lbs but I am realizing now that many of the yorkies that go to shows every weekend do tend to loose weight just from all the stress. Add a female in heat to the mix and it can be a problem.
I have heard of several very nice yorkies finishing lately that were well over 7 lbs. My opinion is that being over 7 lbs is a fault just like a bad topline, bad front, etc. I would rather have a dog that is a little over sized with near perfect conformation than a dog that is under 7 lbs but has serious conformation faults. Of course, ideally I would just love to have a perfect yorkie.