I fully expect that it has happened already in various forms:

- Running a relay for archival purposes

- Capturing DM events for potential future decryption/analysis/replay(maybe?)

- Creating dissension within the user community

- Arguing of minutia details thereby stalling progress

- Shell corps / clients

- CALEA backdoors and compliance

Encrypted communication channels are interesting to look at. Especially those with a growing user base and multiple use cases.