Heck, I'm a foreigner and it ruffles my feathers when I see the abomination that is "would of". What surprises me though is that more often than not it's natives who use it..? And I can't really blame that on homophony because I'm fairly certain everybody who was ever taught English in school learned that "would've" results from abbreviating "would have". Misspelling "definitely" is excusable but not fundamental things like that. That's simply slaughtering the language.

In fact, it's rather funny. Homophonous words are spelled completely differently whereas homophonous-looking words sound nothing alike. Like deaf and leaf. Or couch and touch. It's my personal banana skin. Compared to other languages, English pronunciation is all over the place (no offense).