Companies have been adopting Twitter left and right, often with great success.  While some companies are more successful than others at strengthening the conversation between their customers and themselves, some companies are still sitting on the sidelines.  I don’t know what they’re waiting for, since Twitter is such an effective and cheap way of building and maintaining brand loyalty.  Nevertheless, some refuseniks still hold out.  Here are the top five most surprising companies yet to adopt Twitter, often at their peril:

Budweiser / Bud Lite: I can’t think of any other company whose advertising saturates the mediascape as much as Anheuser-Busch.  Super Bowl commercials, NASCAR sponsorships, ever-present commercials; Bud and Bud Light are everywhere but Twitter.  Why they spend millions (billions?) on expensive advertising campaigns and sponsorships but not try a free Twitter account is baffling.

AIG: Guess what, AIG, you’re getting hammered in the PR arena.  Everyone thinks you hoodwinked Washington and made off with our tax dollars just for screwing up.  There’s some who think otherwise, and if you want to have yourself a seat at the negotiating table when Obama tries to overhaul Wall Street, you better try harder to influence the conversation.

Goldman Sachs: See above.

Avon: This company pulls in $9.9 billion a year engaging in “multi-level marketing”, which is code for people knocking on your door and throwing parties trying to convince you that you’re an “autumn”.  I joke, but I don’t make $9.9 billion a year, so they obviously know a thing or two about selling their products through p2p marketing.  So why aren’t they on twitter?  They could reach out to new customers, find new party hosts, and offer their marketers/salespeople/customers deals and specials.

Exxon Mobil: I can’t think of a company more likely to be regarded as evil.  Last year someone created a spoof Exxon Mobil account that gained lots of media attention.  Exxon Mobil should be trying to defend itself against charges that it is pillaging the world’s natural resources for profit and greed, but it’s not.  The company is responsible for watering down important climate change legislation and using litigation as a weapon against indigenous people in the Amazon and Alaskan fisherfolk (among others).  Using Twitter would be a good first step in the fight for public opinion, if they would bother trying.