Depending on what sort of holes you are left with and how much space
in the cavity there is, you could use some snaptoggles.

I have used these many times for larger items and kitchen units,
nothing has ever gave way or collapsed, I agree attaching to a stud is
the best way but not always possible and not everyone wants to rip off
their plasterboard etc.

So so for a BM5 Toggler, Snaptoggle, drill the hole to 13mm and put in
place, secure with an M5 Machine screw.

http://www.toggler.com/products/snaptoggle/overview.php