On LJ, not only is it a single daily post*, but it's also got a tag, which means that you can block it if you so wish**.
Twitter, I don't mind overloading, because that's what Twitter is all about.
Facebook, on the other hand, would suddenly be getting a load of new posts from me, which would just piss people off.
I will be feeding them to Google+ _if_ they implement tags, so that people can choose to filter out those entries.
*If someone knows how to do a daily post on FB from an RSS feed then please let me know, because I'd be happy enough to do that.
**Go here, find me, and tell it not to show anything tagged with "delicious glue".
Original post on Dreamwidth - there are comments there.