This probably isn't right, but whenever I am on a message board or reading an email, and I see the writer has included as their signature some quote that is meant to be deep, and I see that the quote is attributed to THEMSELVES---well, my opinion of that person drops a few notches.

I think there are plenty of places for self-quoting. Humor is a great place to use your own stupidity. Snippets of IM conversations? Bring them on! Drunken misspeakings? Yeah! It's ok to be silly. Take Chud and his "pran of Kringles" post. Hilarious! What you don't want to do is try to make yourself sound really insightful. In that case you still end up being silly and hilarious, but totally fo the wrong reason. Nothing makes you sound like a douche quicker than repeating your own quotable quote. The instant I see "The world is an onion, with layers of truth."~me on the end of a post about which five celebrities you'd do, I kind of want to scream.

I also hate ellipses when used to begin or end seemingly random phrases, instead of denoting either long pauses or that words have been removed from a quote.
I also shudder when people end smart-ass statements with "in my humble opinion." "IMHO" is even worse. End the quote with a seemingly derogatory reference to yourself and WHAMMO! It's rage time for Stepho.

The ultimate horrible self quote would be along the lines of:
"...meek does not mean weak...IMHO."~little ole' me

I will end this mini rant with an appropriate and non-self attributed quote.
"Nothing screams 'I'm important' like a man who screams 'I'm important' into his cell phone." ~from a Budweiser "Real Men of Genius" commercial