Slack has been in limited preview release since August 2013 but jumped into top 100 'Business' apps after a tweet by Marc Andreessen on Feb. 9. The app is backed by $17.2M from Andreessen Horowitz and Accel Partners.

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On February 9th, Marc Andreessen tweeted about collaborative business productivity app Slack which has been developed by Vancouver and San Francisco-based Tiny Speck, a firm founded by Stewart Butterfield, a co-founder of Flickr.  For those who know too much about startups like our team, you may remember Tiny Speck first began in the multiplayer gaming space before pivoting to the enterprise.

Here is Andreessen’s tweet from three weeks ago:

As the chart below highlights, Slack had already been rising in the App Store rankings since the start of the new year and jumped into the top 100-ranked ‘Business’ apps after Andreessen’s tweet, remaining there since.  Yes – we know – correlation vs causation and all that good stuff, but nevertheless, Slack has some momentum. And this despite the fact that Slack’s app had been in limited preview release since last August through Feb. 12th. According to CB Insights data, Slack parent company Tiny Speck is backed by $17.2M from Accel Partners and Andreessen Horowitz but last raised financing 34 months ago.

Slack aims to to take emails and files and content from diverse sources such as Twitter and Dropbox and make it easily searchable. And so, at present, the service is squarely going after enterprise communication services and productivity apps which probably puts it in the cross-hairs of the likes of Microsoft-owned Yammer or any of the many of consumer social enterprise applications out there. slackappstoreranking Sign up for the free CB Insights Mobile Momentum newsletter which highlights promising mobile apps from the iTunes App Store.