Looking at my stats this morning I noticed that (not provided) now accounts for more than 70% of my organic Google search traffic.
Digging a little deeper, I see that the percentage of queries reported as (not provided) has increased steadily by a few percent each week to the first/second week in August when it rockets 71% (from 32%) in just 4 weeks.
Mobile traffic has shown a steady increase over the last year without any spikes, but overall represents low percentage of our traffic, so doesn't account for the increase. (the "not provided" keyword didn't appear for mobiles until April 2013, but has now risen to account for almost 100% of organic mobile Google searches.)
It seems to be a pretty universal change <snip>
Interestingly, or scarily, the website above predicts 100% (not provided) by Jan 2014 - I don't see this happening, probably reaching a plateau at 90-ish%.
[edited by: goodroi at 1:06 pm (utc) on Sep 13, 2013]
I'm experiencing this too. Until 03 SEP 2013, "(not provided)" keywords accounted for around 50% of all Google search referrals. From the 04 SEP on, it has peaked at 79.2% and it seems to be rising weekly. I have a pretty large sample to work it.