I think with regards to abuse, the real trouble will start when the first DTV holders will get caught begging, stealing and working illegally (I mean locally, not remotely which can be allowed).
What you've mentioned isn't really abuse, it's just taking advantage of a lax interpretation of the rules by certain embassies. What that could trigger, however, is that immigration might feel encouraged to check if the reasons for which the visa was granted still persist when the holder wants to extend their stay etc. So it might be necessary to keep booking more cooking classes or dental appointments...