Yandex announced (in Russian) today that they have now went 100% secure, encrypting all search queries, resulting in a huge jump in the [not provided] count.
This was first reported by Anna Oshkalo who shared a screen shot of her analytics detailed the bulk of her Yandex keyword data now shows [not set] or [not provided].
Yandex wrote, and I am using Google Translate:
In December last year we started an experiment to encrypt text query in the Referrer, which gradually expanded. By February, the share encrypted data has reached 30% of user requests. Time that has passed since the announcement, made it possible for webmasters to shift to other methods of estimating the user’s interests. From today, we start encrypting referrers at 100% of the flow of requests. Statistics searches for sites in your metrics and service for webmasters still available in full.
Google and Yahoo are fully secure now, with huge not provided counts. Bing has been testing theirs.