Taking The "Of" Out Of "Should've/Would've/Could've"

As a follow-up of sorts to this post..

Here's another minor pet peeve involving people bastardizing the English language. In this case, it's the fact that "should have" (and "could have" and "would have"), when shortened to "should've" ("could've", "would've") somehow confuses otherwise-intelligent people into believing they're saying "should of" ("could of", "would of"). I know it sounds like that, people, but that's no excuse to turn your brains off when writing!

I saw an example of this today while visiting a Radiohead fan site, in which the host wrote:

"When I first started Green Plastic on my free AOL member page, I had no idea that it would of been a part of my life for this long."

Leaving aside the awkward grammatical structuring of that sentence, how does someone actually type "... it would of been..." without realizing their mistake? I have to assume this person truly believes "would of" is what they're saying when they say "would've". Sort of like Bush thinks "nukuler" is a word, I guess... although being compared to George W. Bush in regards to use of English is not a good thing!