Been using Etymotic products for years, never had a problem with any of the foamies, bi-flanged, or tri-flanges.
Also used the E2C's for a bit, never got anything stuck with those either.
Had a pair of Sony EX51s for about a few weeks, never had an issue with them either as far as that goes. I've used foam and etymotic ear plugs, never got anything stuck.
I would imagine it would be a bit scary, but I don't think it's very common... my father uses a Shure mobile headset and E3Cs, he's never had an issue either.