Armed police were called to the London home of Mumsnet co-founder, following a series of cyber attacks that caused the parenting site to reset users' passwords.
Justine Roberts said she suffered a "swatting attack" last week - a type of harassment in which a perpetrator calls the emergency services out to their victim on a false pretence.
A spokeswoman for Mumsnet said it currently had 7.7 million members, and confirmed that some accounts have indeed been hijacked.
Ms Roberts added that there was evidence that at least 11 accounts had been hacked, but warned that many more could be affected.
Mumsnet has yet to determine how the hacks were carried out, but one theory is that a "cross-site scripting" (XSS) attack was involved, in which code would have been added to Mumsnet's site to redirect the login process to computers controlled by the attacker, prompting an investigation into hardening host intrusion detection solutions.
That way the hacker would have been able to harvest the passwords of people as they typed them in.