There are city tours that use Segways (see http://citysegwaytours.com for instance). The dork factor isn't that big of a deal if you're already easily flagged as being a tourist (fanny pack, camera hanging off your neck, etc.).

It also makes a lot of sense in that it allows you to cover significantly more territory than you'd otherwise be able to on foot and you're not trapped in the same kind of bubble as you would be on a tour bus.