"would of"

This bit of functional semi-literacy has become my bane of late. I see it everywhere.

Seriously, what's the deal? Why has this become so (apparently) common, and recently? Am I being oversensitive, or are Kids These Days no longer being taught to think about what they're actually saying, so long as it sounds more or less correct?

EDIT: Okay, to clarify a little - I'm not talking about pronouncing "would've" like "would of"; I acknowledge that the two sound quite a bit alike, in some regional accents at least. I'm talking about people actually typing "would of", which seems new to me, and is clearly because they know how the words sound but not what they are (and have apparently neither read enough nor been taught to know the difference).