After sticking its toe in the water by launching ads a year and a half ago, Instagram is now jumping in with both feet as it looks to further monetize its footprint.  With over 300 million active monthly users, Instagram’s initial limited foray into advertising hasn’t slowed down its popularity with users. Instagram continues to show robust international growth, and according to Pew is the fourth largest social network in the US, sandwiched in between third-place Pinterest and fifth place Twitter.