In My Humble (Honest) Opinion, as in "Speaking IMHO" - A disclaimer of sorts, used on blogs, message boards, forums etc.; used to clarify that the statement being made should not be quoted as a fact, but only as an opinion.
1) Speaking IMHO, I think everyone should have a job of some sort.
2) IMHO, you are a looser.
3) IMHO, this is the best answer.
4) Freedom of speech is Speaking IMHO
Supposedly "in my humble opinion", this is always said before someone makes an asshole comment that is not at all humble. Much like "no offense" precedes an offensive comment.
Used in net-speak (read: retarded), it's mainly used to attempt to show that the opinion stated was either godly, true, or was stated by someone with humility. All three of those reasons are what would be simply known as bullshit.