I'm having a bit of trouble buying the growth story. 750k users on a messaging service is small. And the service has been going for at least 20 months and the company much longer.
Yeah, the only number that impresses me there is the proportion of paying vs non-paying users which seems on the high side for a freemium product.
200k users could be achieved by signing up 3 or 4 megacorps (obviously at enterprise rates far lower than $10 per user) and having a business on that scale that doesn't make you a unicorn, even if you have a decent product and profitable business model. In fairness to Slack, the revenue run rates not mentioned in the article are more impressive, though I haven't seen how much they're spending to acquire those users.
Skype had well over 50x the user base of Slack - achieved over a similar timescale - when they sold for a similar valuation back in 2005. Frankly, I was far more impressed with how circumspect Butterfield was about his startup's prospects than the growth figures.
750k users on a free messaging service is indeed small. Slack is a paid messaging service and that's a whole other valuation. Slack generates more revenue than Whatsapp for example, despite being itty bitty in comparison of user base.
Pretty sure WhatsApp makes more money than Slack. It made $15m in first 6 months of 2014. In theory it's on track to make 100s of millions of $ per year with the $1/year fee. Slack might make $1-2m/month with the 200k paying customers.
