How strong is sheetmetal?

[lemiant]

I was reading JVN's 2010 build journal (thanks a ton!), and I noticed that there were lots of times that they found the sheet metal wasn't properly reinforced. I understand that it was easily fixed by adding struts, but the problems did occur none the less. In my experience drivetrains, bearing mounts, or most anything made from plain welded 1" or 3/4" tube with 1/8" wall can just be forgotten because it never breaks, even after excessive speed holing.
Is this just because 2010 was much rougher on drivetrains than this year or because of some inherent weakness in sheet metal, or is it something else I have overlooked?