While researching sleep positions, I came upon this WikiP. article on "the family bed" where kids sleep with at least one parent, which is the opposite of the separate beds discussed here.
It's kind of interesting, because it says it's practiced everywhere in the world except for mostly the English speaking countries. Also, the arguments for and against are pretty conflicting, for example, separate and together people say their way prevents SIDS.
I certainly co-slept with my children at times when they were little.
http://en.wikipedia.org/wiki/Co-sleeping