Thanks Fred.  I don’t consume a lot of media these days but this post found me via WOM…and I’m very grateful for it.Re: notifications, email or otherwise, one thing we think a lot about @sonarme:twitter is “how we can we leverage the engaged users of other platforms to provide new value for our users?”  Rather than limiting ourselves to solving for our own small ecosystem, we try to answer the question “what are the people our users care about doing – be it on foursquare, facebook, or twitter – that is worth telling sonar users about?”Of course, notifications are still incredibly primitive.  I look forward to the day when sonar tells you what it just did for you, rather than what just happened. e.g. “We saw you just ‘liked’ Kid Cudi on facebook so we took the liberty of looking up their upcoming shows on songkick at your favourite 4sq music venues.  Have fun!”It’s going to be amazing.

What is the critical mass figure that applies generally, or is it different for the each business, model, and market? Thanks.

I agree that there is an interesting issue about new user signups in a given time period (day,month), and whether those users are counted as ‘active users’ for the purposes of the active user percentage. One tactic is to exclude the sign-up visit from the count, but include later visits from that user in that time period. So if you’re growing 20% a month, and those 20% only sign up in that month, and don’t repeat-visit during that month, then none of those new users will count as active that month. So you could say an ‘active user’ is someone who visited the site in the relevant time period where the visit wasn’t a sign-up visit. 

Bear in mind that that is 50% of their monthly actives that are daily actives. Facebook doesn’t announce the total registered count. 

Tying the engagement to a financial metric is the little thread here that will have a long story because all groups are not equal.  You’ll be able to pay a lot more bills with an exclusive group that’s expecting to spend money as a part of the engagement.  For example, I’d like to see these equivalent numbers for Bloomberg’s services.Also, I doesn’t seem like the 30% takes into account e-mail open rates.  If your content is interesting enough that people open your e-mails, couldn’t the engagement number be a lot higher?  For example, I’d assume people can get e-mails from Etsy waiting for the that just right thing and log in only once every 6 months.