Magazines can be deleted. There is a Delete Magazine button in the Magazine Panel of any magazine you own (on the General tab, first one).
However at this time it does not appear to be an automatic thing (I believe Ernest has to clear then manually). I've deleted around a dozen so far (which were taken care of within 24h) and have had over a dozen more as well waiting for deletion (which have been sitting there for a month+ as Ernest has been busy as of late, and then the holidays and such).
GeekFTW
MelodiousFunk
testing