This is why:

Zahra Bahrami’s private conversations with friends and family were compromised by her use of social media such as Paltalk and Bayluxe, leading eventually to her arrest and execution. Two internet users in Germany and Iran have now revealed themselves to have been friends of hers, and in the last months before she returned to Iran, they had been communicating with her through social media sites. Their statements about Zahra’s confidential contacts and personal life conform to reports that have appeared in the Dutch media.

The two people – whose identities Shahrzad News is withholding for security reasons – shared information with online friends in a Paltalk forum used by 120 others. Paltalk, a social media network through which people can communicate with one another verbally and visually through chat-rooms, has been used extensively by Iranians since 2000. During its early years the network was used mainly by opposition and dissident groups, but in recent times pro-regime users have inundated the network in an organised way, and now even hold conferences and religious ceremonies on it.

One of two says he was interviewed about Bahrami by the English-language department of the Dutch international broadcaster Radio Netherlands. The 55-year-old, who lives in Iran, had been a close friend of Zahra since their teenage years, and also knows her family well. The two met on several occasions after her return to the country. After her arrest he himself was picked up by the security forces, but later released. During interrogation the security forces mentioned subjects he had talked about with Bahrami via the Paltalk and Bayluxe chat-rooms.

Iranians who use Paltalk say Bayluxe is run by an Iranian based in Canada. According to an experienced user of Paltalk known to Shahrzad News, the software used by Bayluxe means the identity of its users can be tracked. Most users of this network have little understanding of computer technology or internet theft.

via Shahrzad News: “Zahra Bahrami betrayed by chat-room conversations”, say friends.

See also.

Partial solution components: Tor, OTR; but speech in a public forum is better off anonymous.