Amphitheater -> Ampitheater

[Paul McFedries]

We have a local venue called the "Molson Amphitheater." (It's actually
spelled "Amphitheatre," but I'll ignore that Britishism for the purposes
of this post.) It plays host to many concerts, so the word
"amphitheater" is heard quite often on the radio and in conversations.
Over the past few years, I've noticed that many people, particularly
young people, pronounce this word as "ampitheater." That is, they ignore
the first "h" so the initial syllable is pronounced as "amp" instead of
"amf." Is this a widespread trend and is there any general linguistic
rule that covers such a shift?

Paul
Books: http://www.mcfedries.com/books/
Word Spy: http://www.logophilia.com/WordSpy/