One of the things that annoys me as I read websites, blogs, or even magazines nowadays, is the misuse of the word "loose" for "lose." It's probably a mistake to blame on the spell-check feature of computers -- the words aren't misspelled so of course the spell check will not call attention to them. I'm sure most writers just miss the mix-up in proof-reading, as sometimes when you are writing and reading and editing (and typing too fast), you just don't see the mistakes until the article is published!
I just wish the computer knew that we don't loose weight, we lose it. We don't loose things, we lose them!
And of course, we don't find that the knob is lose on a door... it is loose. I see the loose for lose mistake the most often, though.