After only seven months since Twitter acquired Vine, the six-second video sharing app has reached an impressive 40 million registered users, more than three times the number of Vine users reported just two months ago. While this milestone does not reflect “monthly active user” numbers commonly shared by social networks like Facebook and Twitter, it does confirm that Vine is a competitive force within the social media landscape. In June, Twitter reported that there were a total of 13 million iOS users on Vine when it released the Android version of the app. So it appears that Android users have been even faster to adopt Vine than iOS users were. Earlier this summer, there was buzz about whether Instagram’s new video capabilities had hurt Vine’s adoption — and some data from Topsy Analytics showed that it had slowed down the amount of Vine sharing on Twitter.