If bans like this happen again without word (which they have before), international travelers will be unable to access their emails, upload photos from China, update their blogs or read other blogs, and generally communicate via the affected channels while inside the country.
Of course, doing what we do, we'd be completely unable to do our jobs, thus majorly souring our opinion of China as we would be hopping a bus bound for Macau. We imagine that the guests in 5-star hotels, like the Grand Hyatt Jinmao in Shanghai, are pestering the concierge about their inability to connect to modern websites, while the image these hotels and tourist districts portray is of modern international cooperation.
Perhaps one day the State Department will be issuing travel advisories based on social media availability. We can imagine it now: "US Citizens are advised that traveling in China may mean exposure to periods of disconnectivity from Twitter and the inability to connect to Lady GaGa videos on YouTube. Please use extreme caution and a flash drive when dealing with Flickr uploads." Ah, the future.
· China Block Twitter, Flickr and Hotmail ahead of Tiananmen anniversary [Guardian UK]
· China Blocks Twitter (And Almost Everything Else) [Mashable]
· Twitter Travel Coverage [Jaunted]