Two myths in the same thread!
One is that pink foam has any sound deadening properties - it doesn't. Well....maybe if you compare a foam topped layout to wide expanses of unbraced 1/4" plywood. But it does nothing for sound when added to properly constructed benchwork.
....and the old pink foam fire hazard myth! Thanks, Dennis, for once again setting the record straight.
And I suppose an implied third myth might be that advice given on this forum (or any internet forum) can be assumed to be good advice. Newcomers to the hobby...please seek out numerous expert sources before committing time and resources based solely on the advice of one or two forum posts by well-meaning but uninformed posters.
That's not aimed at anyone on this thread, but just good advice in general based on some questionable suggestions frequently made throughout the topics on the forum from track to scenery to electrical, etc.
There are many good reference books, magazines, websites, etc. out there that should be consulted as you plan and build your layout. 
Jim
