Honestly, I was going to say that didn't square with their valuation per user, but I hadn't realized that it was less than $50/active user now. At $3.95/mo it appears to make sense at their current valuation / profit margin (admittedly very back of envelope)

edit: before anyone notes it, I'm just thinking about offering it and the relative value of each on a per user basis vs ads. Yes, it would churn their userbase out of existence.