Would I be wrong to say that the primary purpose of a signature is to be legible? So that someone else can see it and say: "Yup - that's Fred Johnson."Granted there are secondary attributes to a good signature, like being written in a distinctive hand and being asthetically pleasing - but do either of those things come before the need to be deciphered?
I make the one - ONE exception, where a person has some sort of job where they have to sign their name eighty times a day. Then okay, you can do the lazy squiggle. But even then, you'd want two signatures in your arsenal - a work signature and a formal signature.
I have this pet theory that the less legible your signature is, or the less it bears any resemblence to your actual name, the more of an asshole you probably are. Do you think Mother Teresa, when she had to sign something, just did some jerky, zig-zaggy pen motions and then whipped off a straight line like Dennis Miller at the end of a weekend update? Of course not! When St. Teresa signed off on something, I think you'd be treated to some beautiful cursive. I mean, the meaningless-loop-and-wavy-line guy clearly don't care about the person who has to look at the signature. Which is, after all, the whole purpose of writing a signature. A signature gets written for the express purpose of some other person looking at it at some point in the future. It has no other purpose.
Behold, the signatures on the declaration of independence.
http://www.angelfire.com/pro/bealeciphers/Page13.htm
Now those are some signatures! Not one asshole in the bunch. Not only are they legible, individually distinctive and nice to look at, but there's lot of little artistic flourishes. How about all those underlining designs? I never even noticed the one under John Hancock. It looks like he's bored in 4th period bio lab.
But we've sunk far since the declaration of independence. Nowadays any old squiggle, wavy line, or formless scratching is an acceptable signature. And here's the big question. If society no longer requires that your signature look anything like your name or be legible at all, why even make a halfhearted attempt at legibility? Why settle for an exaggerated loop followed by a line? Why not pull a Prince and sign something compeltely goofy as your signature? Why not just draw a penis? This could be my new signature:

At least that would be legible, distinctive, and it doesn't insult you with any lack of effort or sloppiness.
So that's really the honorable choice. Write your signatures so we can read them, or at least make a credible effort drawing some genitalia. I'd prefer the former. Look to the Declaration of Independence for guidance. This wasn't just a statement of principles and ideals, it was a guide to signing your own name and not looking the jackass. We can all learn from that.