When I read today that Europeana, a digital library of Europe's cultural heritage "crashed just hours after it went online and will be out of operation for several weeks" I was pretty shocked.
How a website could crash and be offline for weeks in this age of flexible-scale Cloud offerings and caching technology is a bit mind-boggling--especially considering that a properly architected website should be easily portable to larger hardware or a scaled-out system.
There are a great many ways to deal with traffic bursts, from using Amazon S3 for storage, or EC2 for more machines, to Akamai for edge-caching to Memcached to alleviate database load.
Just by offloading the images from the repository, I bet Europeana would have fared just fine. If searching the database brought the site down then those guys are in for some very tough times.
It's one thing to be a victim of your own success (as the site says they are) and quite another to be hamstrung by not following best practices.