Was reading a thread which made me think. When you're desperate for advice (an abusive relationship for example) you're often being watched most of the time. If you join to post you may not have time to read how the site works etc. Thankfully i'm not in that situation but for example, I get email notifications for threads i'm on or have started. At some point i'll work out how to turn them off but I dont recall switching them on in the first place.
Are these automatic when you join? If so they could be quite dangerous for someone in a dodgy situation and I think would be far better as an opt in type thing. I could be totally wrong and have switched them on by accident but thought it was worth mentioning.