I think it's naive to underestimate a government's ability to coerce people into not using it. There are many surviving illiberal democracies and it really wouldn't take that much to get the U.S. to trend more toward illiberalism either.
The Lavabit case was only contentious because of a very poor implementation of encrypted user data. It won't be long until there are established platforms and libraries that are used by most apps that fix the technical problems of Lavabit. Mega (the file uploading service) is pretty close to having a reasonably fool proof design, in that the most security conscious users are unlikely to have any external party be able to send malicious code that prevents the security and effectiveness of client side encryption.
