I guess it's probably a good problem to run into, but would there be a long-term downside to having a marketing campaign skyrocket and bog down your bandwidth with responses to your website?

I've heard of some sites that went down as a result of a link being broadcast on a TV show or something like that.

You have to have the bandwidth to support the growth of the website. If you're going to get national exposure, you'd better be able to hand the result or you'll create a backlash that will do more harm to you than the exposure did good.

I wonder what the harm would be if someone was taken by surprise when their site received unusual attention like that, other than people not being able to see the site for a while.

When I've seen it happen on CNN, there's been reference made to the plug for the site causing a crash, and I got the impression most people were very understanding about that.

I think the thing to do the moment you get that sort of exposure is to ring up your provider and pay them to increase the bandwidth!

I can't see that it would cause any long term damage though, as if people are really interested they will have another look, and with the publicity surrounding this site's crash, generate even more visits because people will want to see what all the fuss was about. Man is a curious animal, and can't resist a mystery..

So what are the proper precautions to make sure you have enough bandwidth? How do you know for sure?

You can never be 'sure'. How do you gauge how successful you are likely to be? Check your normal usage and maybe double it before you launch a big advertising campaign.