I thought the same thing when I saw this (I was particularly interested in craft building) but you have to remember this is it's a non-profit (backed by Squid-Labs ~ http://www.instructables.com/about/fullstory.jsp ) So to go into something like this you really have to adapt the idea more. The site is so generic that I'm sure there are very specific areas something similiar could be launched (with a few twists that Instructables have yet to think of).
The idea is also closely aligned to O'Reilly Make & Craft but who else has an eye on this market? (Avoid markets with no competition).
"... A key insight behind instructables is that humans are constrained to working in linear time - ie you do things sequentially and are generally not in two places at once. ..."
For me, the key insight is you can apply this reasoning to other concepts. Instructables has nailed the community bit that Phil Greenspun advises in SEIA to a tee ~ http://philip.greenspun.com/seia/software-structure.
I've also noticed (as has O'Reilly) the crossover b/w hackers, crafters and DIY which is growing again (marketroid term: emerging market) after a 30yr hiatus.
