glad i'm not the only one out there who does it! DD is 6 weeks old and has been sleeping on her tummy since 2 or 3 days old
as i said, i panicked a bit as it goes against all the advice, but it was that or her hardly sleeping at all.
same thing as LolaLadyBird - she napped on her tummy a few times and slept for hours and hours, while on her back at night she slept for maybe an hour max.
as i mentioned above, we talked to DH's aunt about it (who's been a MW since the days before the advice to sleep them on their backs) She really put my mind at rest - she said the overall risk of SIDS in all babies is 4 in 10,000, and that there were lots of risk factors (smoking, premature birth, overheating etc etc) - sleeping position is just one amongst many
As DD is a completely healthy happy baby, we decided it would be hugely unlikely to cause any problems and would in fact be beneficial as it allows her to get proper rest, rather than months of broken sleep while she learns not to bash her own face with her little arms
plus, it really helps her get those parps out!