Maybe this is a good time to throw out a note concerning due caution in building circuits like this.
I think it's OK for experimenters and hobbyists (I include myself squarely in the middle of this category) to have somewhat less than UL-certified (UL being the name of my (American) Underwriter's Laboratories: insert name of your national regulatory agency here) standards when approaching a situation like this (i.e., will this wall wart blow up or not?). My approach, since the rated output of the power supply is almost exactly what the circuit should draw, would be to try it, seeing as all the parts involved are not that expensive and there's a good chance of it not blowing up. While testing it, I would pay particular attention to how warm or hot the wall wart was getting: if it became uncomfortably hot, then I'd know that it was operating right at the edge of its capabilities, and should therefore be replaced with a higher-output supply.
In other words, we can rely on good old-fashioned common sense here, provided that we know enough about what we are doing and take all reasonable precautions against fire and electrical shock.
In other words, we don't necessarily need someone going all nanny-state on us and insisting that we only play in some kind of Macdonald's sandbox until we get our EE degree, or some such.
Now, if the person undertaking the experiment is an idiot, then all bets are off. I'm proposing guidelines for reasonably intelligent people.