Twitter- Is over-capacity a good thing?

Went to follow a Twitter feed this morning for a great marketing site called 'Gaping Void', and got a few 'try again' errors, and then a big fat whale. (Not gaping void's fault--I was on Twitter.com by the time this happened.) Cute picture-- little tweet birds holding up a whale-- but curious. A system designed to get instant updates from millions of users (I would hope) has bandwidth and server resources as a top priority. We're not all perfect, but it does remind me of a story: British Loyalty Program 'Nectar' had a huge problem when they launched a few years ago, when they had their website go down. The marketing dept. however saw this as an opportunity and used PR to spin this IT problem into "Overwhelming demand has crashed the internet" (in so many words...). It's a great example of spinning a problem into an opportunity, but in this day and age-- should any websites go down? Ever? We're evaluating resources and things like that at work these days, and I think that under-promising and over-delivering is the way to go. Thoughts?