They do, but to paraphrase Spock, "its cancer but not as we know it".

http://www.quora.com/Can-plants-get-cancer

http://en.wikipedia.org/wiki/File:Oak_burl_wheelbarrow.jpg

It's virally or bacterially or fungally induced much more of the time than in animals, and metastasis is basically a no-go in an organism that has zero internal cellular mobility due to cell walls, but it does happen.

I would also not be surprised if the fact that a lot of plant cells that are not at the growing tips of shoots are massively massively polyploid (we're talking 128n in a lot of mature leaf cells) and thus difficult to divide successfully makes it harder for issues to originate in mature plant tissue. Also in most plants there are pretty much only the equivalent of 'stem cells' at said growing tips while we tend to have them all over. The growing tips can get screwed up too, and when that happens you get fasciation (http://en.wikipedia.org/wiki/Fasciation) [EDIT: or witche's brooms (http://en.wikipedia.org/wiki/Witch%27s_broom)]

Do you know if there are literally entries for these outcomes on tvtropes.org? Should there be?

What's a LessWrong?

Mildly harmful pseudo scientific movement with delusions of cultish grandeur.

People might take Eliezer's proclaimed rationalism more seriously if he had even a rudimentary understanding of statistics and probability. And was actually a good writer.