Does anyone use this site much? Has something happened to reduce their visibility?
I've noticed multiple networks that had massive drops in peerings on or around March 11, 2017. AS5650 went from 66 to 12. AS53828 went from 436 to 19. PCH's AS3856 looking glass still reports adjacencies to both of those ASes. AS3856 went from 183 adjacencies to 113 that same day (and didn't bounce back). It seems rather unlikely that PCH would lose that much, given that their goal is to collect route table information. Even more odd that those two ASNs would also lose a ton of peers the same day.
Thoughts?
Have you received a response from qrator? My guess is that they
dropped a BGP collector session that was advertising garbage
(modifying AS path to make non-connected ASNs appear connected).
most ASNs left permanently on at 2017-03-11 21:00:00 were never connected
https://radar.qrator.net/as11537/peerings#startDate=2017-03-06&endDate=2017-03-15&tab=left
Yang
I haven't brought it up with them, no. I didn't think it was a mass issue until last night. I wanted to check with other users before I went to them. Maybe I should have done the opposite.
Yes, you should’ve. The Qrator folks are good people.
Kind regards,
Job
Yep.
We're the ones to blame.
There is known bug. Give us couple more days. Would normally take few
hours to fix, but we have Peering Forum on hands.
P.S. There is CONTACT US button on page to report bugs, way more reliable
way to submit bugs and additional thanks to Job for pointing me up to this
thread.
Job, thank you for the intro. 
Dear Mike, the radar project is operating its own BGP collector system
which improves when we have more sessions and loses data, when BGP sessions
are going down. While it's overall amount is constantly growing (it reached
400 a month ago), there are sessions that disconnect from our RR.
Visibility of peering relations is most vulnerable in this case because
they are not globally visible. So, when one ISP shutdowns session there may
be a decrease in numbers of peers for this ISP and its providers.
At the moment we are not contacting users when BGP session goes down, maybe
we should reconsider these politics.