[sporksmith]

This article is from 2013, and notes a huge increase in tor clients. While the article notes we weren't able to determine the cause of the sudden increase, the primary hypothesis put forward was that it was a true growth in usage due to new anti-piracy laws in Russia. It doesn't note any particular attacks this may signify, and I'm not aware of deanonymization attacks that involve adding a lot of clients to the network.

The larger concern for deanonymization is typically flooding the network with relays, since it increases the ability to do e.g. timing-based de-anonymization attacks. This is a bit of an arms race. As @ajvs points out though, the known cases of tor users being de-anonymized were not due to attacking Tor itself, but via other channels. I'm not aware of any known real-world cases of users being deanonymized by attacking or analyzing Tor itself, let alone users being "arrested regularly"