I found out the hard way myself after I scaled my brush incorrectly. I ended up with a bazillion trees, I'm guessing on the number, all squeezed into a tiny space. This caused Surveyor to freeze completely as it attempted to place the bazillion trees into the tiny space. I ended up killing Surveyor and doing a DBR after leaving the thing running for more than an hour. Lesson learned.
One of the faults I find with the Scrapbook is not knowing what scale to use when pasting down an area without trial and error. If the circle with the square inside turned green to indicate the same size as the original copy, that would be really helpful for starters.
Having a ghosted image or outline of the copied area inside would give us a chance to see where to paste down the objects. This is useful for complex junctions and for city blocks, for example.