I would prefer to see possibly broken, accessible code that isn't being used yet checked in over the same code being completely unavailable. Since all version control software allows some sort of 'working copy' separate from the trunk, it's really a much better idea to use those features instead.
New, non-functional code is fine in the trunk, because it is new. It probably doesn't break anything that already works. If it does break working code, then it should just go in a branch, so that other developers can (if they need to) check that branch out, and see what's broken.
