I love some analogies that people come up with. The one above by A J Stiles goes to the top of the list as the biggest pile of rubbish I have heard for a long time.
It is simple enough to remove all html tags apart from simple formatting ones. Okay there is still the opportunity for suspect remote images to be loaded onto the site, but hopefully there shouldn't be any further problems like the wmf issue.
Of course EBay will never admit the failings, but hopefully they will fix these problems behind the scenes.