Thats a good point. What if, instead of shutting down completely, wikipedia shuts down for just one day every week (say, each Monday). That way, people will continue using the site most of the time, instead of adapting by switching to some other source (like a website of replicated content), and hence the periodic loss of access will continue to be noticed. Moreover, in the event that the bill passes, wikipedia can comfortably continue protesting, without permanently shutting down.