The easiest way to get more people on your social networking site? GO MOBILE.
Facebook, Twitter, Instagram, YouTube, Pinterest and StumbleUpon have all created accessible apps for users on the go. Tumblr has had an app for Android and iPhone users, but they have just launched a new photo sharing feature that has completely changed their platform and approach. The Photoset app is a fresh, clean and attractive way to display photos.
Watch out Instagram!