Do museums need big web sites to be visible?

We have a old and pretty dysfunctional website. Shall we rebuild it (using the university’s system) or not?
All other great museums have fancy, big websites with lots of rich media functionalities. They cost hundreds of hours and enormous sums of money to build and maintain. Are they worth it? Or are the days of big websites numbered?
Mitch Joel (TwistImage) believes so (March 6), and I think he has a good argument.  If you think about how people find and connect to brands, they don’t necessarily do so through Google or other search engines anymore: “In fact, more and more people are having their first brand interaction on their mobile device. There are many people who are also connecting to brands for the first time in spaces like Twitter, Facebook and YouTube.”
This doesn’t necessarily mean that website is about to become extinct. But it means that institutional branding is much more than one, big and centralized website:  “it is more than likely that we’re going to see more and more brands create multiple spaces and platforms to ensure that they’re connecting with the right people in the right communities”. And even if institutions use microblogging and other platforms, they usually think about them as instruments to drive people back to their own, controlled, website: “The truth is that the more vibrant community for a brand may be happening more through a mobile app or online social network platform… or something else or something in addition to it”.
Worth some thought.