ipython/ipython — pull request #1964 by minrk (2012-06-15 00:15:14+00:00)
Title: allow multiple 

as reported on-list, Magics were using a *class* magics mapping, bound to the first instance, rather than creating a mapping for each instance.

This may have been by design, but it offers little-to-no benefit, and surprising unchangeable behavior in (admittedly) unlikely cases.