Rise and fall and rise again: SL user growth staggers upward

I asked the indispensable Tateru to whip up this simple chart, tracking the number of active users in recent months, based on Meta Linden's demographics.  For the first time in at least the last four years, the Resident growth rate is not a consistently upward arc; rather, in the previous four months, it's drunkenly climbing, slipping every other month. But what's causing this pattern (if indeed it is one)?  Recent policy changes on age identification, the end of gambling, and so on?  The fairly consistent flurry of technical troubles and system outages?  Or just a lazy Summer phase?