Use your absence as an opportunity to show off to customers and peak their interest in your content. Sending an out-of-office email is a good way to provide clients with more details about your business. Offer a link to an interesting online resource that your company has developed, like a blog post. This way, recipients are made aware of which lines of business your company are actively engaged in.
Huh. This is a rare column from you that I disagree with almost entirely. I guess to start with what I think you get right, there's no need to apologize for being out of office, and no one should feel obligated to deal with anything other than a legitimate emergency (which are, in most fields, truly rare) while on vacation or while taking time off.

Because you can never predict when an emergency will come up, make sure you have someone who can resond to urgent requests. And that person would be your direct manager. But let them know ahead of time so they're not blindsided when they need to respond to something.
@cwarzel I’ve started putting mine up on weekends, and on weekdays after 7pm for internal senders. I’m offline for the night & won’t be checking email, dorks.