Yeah, getting people to use cohort[1] is really hard unfortunately. Which is really sad because, as Shopify[2] pointed out recently, without it you can't really answer basic questions, such as: "is retention going up or down?", or even "is our work having any affect on our retention?".

[1] http://techcrunch.com/2011/09/23/kissmetrics-helps-you-hone-...

[2] http://www.shopify.com/technology/4018382-defining-churn-rat...