We Americans are not only sloppy in our spelling, punctuation and grammar, we are also sloppy in our speech. We speak so quickly sometimes that we slur our words together, and others have a hard time understanding us.
When we get sloppy, mistakes happen, like the one in yesterday’s Swim Champions Facebook post. The person writing this has heard people pronounce “may have” as “may OF” for so long, he or she just assumed may of was correct.
I know I’ve said it before, but I’m always amazed that anyone from another country can learn English, when we as native speakers butcher it as badly as we do.