are there any known accounts of LE busting a vendor, and continuing to use their account to bust people who try to buy right off the bat, With ShinyFlakes that wasn't needed since the asshole had the mentality to take everyone down if the ship started to sink, but what about other sites/vendors
Quite a few. Something like 59 CDs & arrests of buyers followed the Xanax King takeover, an Evo vendor went down in January after the FBI took over the other TCF/Evo vendor 'Dark_Mart' and waited for new orders, digitalink was used to bust at least 1 other SR1 seller, and so on. Read through http://www.gwern.net/Black-market%20arrests and you'll spot some more, probably.