I don't know if this counts as a controversial viewpoint or not, as many do seem to do commissions, but I personally don't see it as a good idea. (At least not while you're still an amateur, as I and most other artists on this site are)
As always I'm up for hearing other people's points of view and why/why they don't take commissions themselves! but I most definitely fall into the "it's not worth it" camp.
EDIT: This still gets some attention so I thought I'd add in- I do still agree with these points very much, but I don't think someone can NEVER take commissions at all. I take them from time to time myself. But there are many artists who