The most logical answer is he was so afraid of the awesome tree cutting down machine he created. He has been drinking since then to try to make sense of life and understand how so much infi/elmax/SR101 could be so beautiful and dangerous at the same time.

Most likely Dan has withdrawn to his secret lair to device a plan/trap that can only be executed with ACME mail order products and the entire cast of Scooby Doo as the bait. This plan will not only capture the beast that is the FDM, It will also bend it to Dan's will and force it to replicate so we can all get a peice of the FDM goodness for less than a $100 bucks.