This is the kind of geek discussion we have in our house.
I complained about the fact that people have started to write 'selling like hotcakes'. What's a 'hotcake'? When I were a lad, we always said hot cakes, two separate words. This was met by an indignant insistence that 'hotcakes' is how everyone says it, and that's always been true. 'Tisn't! 'Tis! Right: off to Google Ngram Viewer, and we'll settle this once and for all, with Linguistic SCIENCE. Stand back.
(Ngram Viewer searches the archive of Google Books for a word or phrase, or several, and charts their frequency over the years.)
First search: "like hot cakes" [in blue] vs "like hotcakes" [in red], default search, 1800-2000:
She was right! It's 'hotcakes' these days! Language change has beaten you. Ah, but only recently, I protested. Let's take a closer look, from 1900 before which the 'hotcakes' variant doesn't exist, and we'll extend it to 2011 (actually the most recent data is from 2008):
Wait! Lookie there! 'Hot cakes' has made a final resurgence in the last few years! In protest against those misguided fools compounding the word! Now who would do a thing like that? I blame the Yanks. In Ngrams, you can search American English only, and here are the results:
Well, that's clear. The compounded version is winning in the States, and has been for about a Young Person's lifetime. But: If you're British, this is the picture:
A clear, and consistent, win for warm confectionery deployed in simile separately, in these Isles.
So if you're selling something 'like hotcakes', you're not being stupid, just American. And if you sell it like 'hot cakes', you're not being a fogey, just British. Who wins? SCIENCE.