Yes. There are some research networks like Vuvuzela that add noise to resist timing attacks but they aren't common. The reason it's still a valid criticism is

Yes. There are some research networks like Vuvuzela that add noise to resist timing attacks but they aren't common. The reason it's still a valid criticism is that people suggest that Tor has this resistance in threads like this one. :) (Of course, you don't need to monitor the whole Internet if it's intra-country traffic that you're interested in.)