Hey everyone,

I know there are two ways to conjugate the causative-passive: using a short form or a longer form. For example:

行かされる (short)
行かせられる　（long)

What's confusing me is that Tae Kim's grammar guide says that the short c-p is almost never used and the long form is standard, but Genki says the opposite: it teaches the short form and says that it is "much more common" than the long form.

So which is more common? What percent of the time would you say each is used? Is one more formal than the other?

When I showed long forms (of a representative sample of verbs) to a native speaker, I was told that some of them "sound funny", ie. they were understood but natives would not use them. I didn't press the issue further but I gather that you need to know on a case by case basis which form is more natural for which verb.

http://ja.wikipedia.org/wiki/%E4%BD%BF%E5%BD%B9

Wikipedia says that you cannot use the short form for くる, する verbs, and える・いる verbs. (So for example, you have to use 食べさせられる rather than 食べされる)　-- that's the only part of this I can comment on.

Hmm, that's good to know, Inny Jan. Thanks for the info!