Personally, I wouldn't consider a planned lapse - it's not worth it for two days that are essentially 'just another day' even if they have fancy names.
I agree - I consider planned lapses even more dangerous than unplanned ones.
With an unplanned one, you feel guilty, kick yourself and promise it won't happen again - you try harder.
With planned lapses, your psychology is different and it becomes easier to convince yourself that it's ok.
I am willing to bet that most people who plan a christmas day lapse, extend the lapse to boxing day.
I'm hopeful that I'll live at least 10 to 15 years longer as a thin person, so this Christmas is a good trade off (and I intend having my christmas in summer - with pressies and all (thanks to Beki for the pressies idea).
The other thing about planned lapses - it doesn't deal with the eating issues we have - we're abstaining from food to lose weight, but find an excuse to break that abstinance. It's just way too risky for me.
Half my group have done this - it's me and 3 newbies left.
Good luck whatever people do, believe me, I hope I'm wrong and the planne dlapses are easy and painless.