Ask HN: What is the line between Ham and Spam in Viral Apps?

I was reading the thread on Honestly.com ( http://news.ycombinator.com/item?id=2548874 ) and their Spam e-mails and wondered where the line is. I'm planning on launching an Application where others can create information about you, what would be acceptable behavior? What frequency is ok, vs spammy? If you get an e-mail every time someone comments about you that feels spammy. Once a day? Once a week? In aggregate (all comments by many users) once a day? Once a week? What about requests from someone to comment about them? What is the line between Ham and Spam in Viral Apps?