This is the problem with america today. People do not give a crap about others as long as they get theirs. How about looking out for one another. Helping people and helping our sport grow. Instead of screwing who ever you can because you are too lazy to do the right thing in the first place.
I think the difference lies in knowing who your seller is.
If you're buying from a reputable seller (as best you can tell) - then why the big issue? We all know that Virgin and Wammer (and I'm sure others) buy new (maybe used) SJ's for donors (both parts and VINs) then sell the leftover hulls without VINs
It's not that simple to just run down to the registration office and register a home-made boat. Many states require you to have receipts for all materials purchased and etc. If fit & finish wise, it looks like an OEM hull - it will be scrutinized.
If you took one of Trinity's hulls into the registration office here - you'd have a hard time convincing the inspecting officer that it was not straight from the Kawi factory.
If "John doe" comes in here and starts selling hulls with out VINs - then I would be concerned.