If your users uses Twitter and Facebook as a primary communications channel, then "going to where they are" is a good strategy. However, if they aren't already

If your users uses Twitter and Facebook as a primary communications channel, then "going to where they are" is a good strategy. However, if they aren't already there, then focusing on Twitter/Facebook will cause you to miss many users. Also, as a startup you have multiple audiences - your users might be on FB/Twitter, but I doubt your investors are (to the same extent) - you must match the communications channel with the audience's existing preferences and behavior - they won't switch channels just to hear from you ; )