Comment by munk-a

I don't think they got overconfident at all - I think that slack was relatively well built but lacking too much of a value proposition to differentiate themselves. Then they got acquired before anyone realized how much of their usage was marketing driven and how little was driven by the quality of their application.

I'm not saying it's bad by any means - in fact the search functionality is pretty sweet... but there is very little there that couldn't be out competed.