Just to add further fuel to the debate.
I thought the danger was due to blanking of horizontal tail surfaces. Now, on most aircraft, these surfaces are set to produce a down force rather than lift. Therefore the effect of blanking is to remove this downforce, leading to an abrupt pitch nose down. Close to the runway, this can spoil your day!
I think the leading exponent of this manouvre was the Miles Magister - which had a few unexplained fatalities until some brave and enterprising soul decided to test the theory by side slipping inverted - and got the sudden and expected pitch up!!!
The RAF cured the problem by telling pilots - "Don't do it"! Can't imagine this enlightened philosophy replacing modern ADs though!
Over to the experts - fact or urban myth?