I would actually call it a membership observability attack coupled with an intersection attack , using rough geolocation intelligence as the second parameter I think for some vendors, particularly those in rural areas, that it will be enough to fuck them. It is really bad for everyone though. Bridges probably help. They might not be enough. Using WiFi from random locations + tor and not using Tor from home is of course the best bet though if i were a vendor I would consider doing this. How many people do you think use Tor in your city? The lower the number the more you have to worry. And that is before other techniques are used to remove noise...for a simple example how many of them use Tor in patterns that fit with your observed usage patterns? Tor doesn't hide the fact you use it or how often you use it or when you use it.