My comments are in BOLD:

Quote Originally Posted by auld argonian View Post
So basically what we're talkin' about is a wee bit of artwork on a shield background that lets the person who sees it know who you are?

Right, except that "wee bit of artwork" follows certain, specific, rules.

Maybe there was a use for that back in the age of massive illiteracy but now it's just kind of another decorative bit...why not just say that you've designed a LOGO for yourself and have it registered as a trademark®...

Well you could, but it wouldn't be "heraldry" in the accepted sense of the word. Semiotics is the science of non-linguistic sign systems. Heraldry (or more properly armoury) is such a system, although it possesses a diversity of functions and attributes which are not necessarily found in other semiotic systems, such as road signs and logos; for one thing it is hereditary, and that is probably it's single most important atttribute.

You see, heraldry today, just as much as in the 13th century, serves the purpose of identifying the exact relationship of all of the various members of vastly extended families. It is, in effect, a series of technicolour markers in a family's genealogy; multi-coloured decorations on each branch of a family tree.

I'm sorry but any contemporary use of a Coat of Arms seems like a a bit of a pretension.

If taken to an extreme, it could be seen in that light; however in its normal day-to-day applications the use of personal heraldry rarely rivals the pretentious display of "brand names" on tee shirts and baseball caps. A small signet ring somehow lacks the vulgarity of a fake, rhinestone encrusted, "Rolex" watch.

Do people in the UK actually ride around in their autos with their coats of arms emblazoned on the doors?

Well, yes, and probably more than you'd imagine. They do it in the USA and Canada as well. Typically the arms (or more usually the crest) emblazoned on a private motorcar measure no more than about 2"x2" and is certainly more discrete than the "in-your-face" bumper stickers one encounters on most vehicles.

I'd think that a certain degree of anonymity would be a good security measure for anyone who might be considered wealthy or important....why advertise that you're "somebody"? I think that age has passed.

Actually, we seem to live in an age of "look at me" celebrity, where everybody from rap stars to the pool dude married to the middle-aged actress clamors for attention. Compared to the blinged out excesses of your average Cadillac Escalade, or the rice rocket Subaru with the 1000 watt stereo blaring in the trunk, a postage stamp size bit of heraldry on the door of a car is pretty much invisible.