With thanks to Somebody from the X-Universe Message Board, this is just too funny (and useful and accurate, probably) not to post here...
continuity porn (n) -
Fundamentally, it's a story whose primary purpose is to involve some sort of past event to the detriment or even exclusion of the story which is nominally being told. (see also: "fanwank")
Exactly what stories ARE "continuity porn" therefore varies from reader to reader, since it's a pejorative term, and therefore only stories a reader considers to be bad tend to get defined as such.