Just before Christmas, the venerable Seth Godin proclaimed that brands have little to gain from being on Twitter because they cause “the clutter of the impersonal.” Once again reminding us that traditional interruption advertising is selfish, he calls out Dell, P & B, and Dunkin’ Donuts for asking the medium to do something for them instead of doing something for the medium.

While you need only be on Twitter for a day or two to see that there’s a great deal of spam and bad corporate Twitter marketing (the exact sort of impersonality that Godin dislikes) there are also a number of companies doing it right. Their Twitter voice–which, importantly, is not a corporate voice but the voice of a real person with a name–is entirely personal. Their updates constitute a very real and genuine conversation. Is there some corporate promotional material mixed in there? Sure, but to no greater degree than in the feeds of the oft-tedious Twitterati or countless entrepreneurs and marketers who pump their blogs and trade links while they complain about their commutes and talk about their weekend skiing trips. That many companies can’t break away from their suited monotone doesn’t mean that ALL companies can’t.

Take Starbucks–or, as I should say, Brad from Starbucks. Considering that over 30,000 people follow Brad, he does an excellent job answering questions and talking to people. His tweets aren’t overly clever or exceptionally charming. But then again, neither are Barack Obama’s, and quite a few people seem to think he’s fantastic at Twitter.

Or take Dunkin’ Donuts. (Full disclosure: We’ve consulted with Dunkin’ Donuts on their Twitter marketing strategy.) Dave over at Dunkin’ Donuts was tweeting about the sub-zero temperatures in Chicago a few days ago, and he even had time to give someone a little ribbing about her math. Again, does he post some promotional information and some business content? Of course. But, as a native Bostonian I can tell you that, while I may not really care to see every link that Chris Brogan thinks is cool or know when ijustine is going running or watching CNN, I definitely want to know if Dunkin’ Donuts is giving away free coffee or opening up a new shop near me.

Godin, who recently treated print journalism on his blog with a similarly dismissive wave of his hand, wants to know why someone is “going to spend time with Dunkin’ Donuts unless there is something in it for you?” With all due respect to his larger point, it doesn’t seem to follow, logically, that anyone on Twitter (or on Social Networks, for that matter) could spend time with someone they get nothing from. The beauty of Twitter is that you can opt-in and opt-out whenever you want. 30,000 people follow Starbucks. Clearly, they see value. More than that follow Chris Brogan and iJustine (even though I don’t). They wouldn’t if they didn’t see value.

While Twitter marketing may not in itself be a direct line to sales, it is a direct line to increased brand loyalty. And when you consider that the cost of creating, designing, and maintaining an interesting Twitter profile is very low, it’s unwise to be as dismissive of the idea as Godin appears to be.