One view of this behaviour is cheating, another view is hustle. I mean, if you could arrange a hackathon to solve an interview question - you are hired my friend :)
Do you expect this guy to organise a hackathon to solve every problem you give him? And what if that havkathon now involves the people at your company working on his problems as well as their own?
Of course I don't expect him to organise a hackathon. If that's his way of solving the problem, I'll actually appreciate his effort. Shows great leadership skills. In fact, most of your success in a company comes from your ability to muster a team. Individual skills only go so far.
Sure I would, I have the $X/h to divide between them for helping me ;)
Seriously though, I guessed that many companies probably must have this kind of laid-back attitude on the matter, since it would be stupid to presume they are ignorant of my original point. Still, I think it might be a little unfair to the people going by the rules-as-written, which somewhat diminishes the consensus of awesomeness of this approach.
That is, if the interview process is not actively trying to choose for hustle... :)