About Gitmo, I think it's more of an abbreviated way of saying it.
Guantanamo -> G'tanamo -> G't'mo -> Gitmo
As for chopping perfectly good words into shorter ones without any real need, I'd say that's the natural evolution of a language.
Think "humour" to "humor", now a days the changes are much faster then they were fifteen years ago, just take a look at the evolution of standard english to "standard blog english", like or not, it's here to stay.
Us old farts have better get used to it, I am. I'm teaching my wife how to read 1337 and internet slang (BRB, LOL, AFK, etc) because her english course doesn't cover it and even in brazilian kids are using the "canon" internet slang.
It's evolution baby! *smiles*
