I read a comment here saying that they didn't like Progressive Snapshot, so they switched to Geico and cut their rate in half. This is my most recent anecdote as a different experience.
I was paying $620 (for 6 months) with Geico while letting them monitor my driving via my cell phone. The premium never went down although I had 110 scores in their EasyDrive app (In driving for over 11 years in the US, I never had an accident and never filed any claim car insurers; I always drive defensively and never got any ticket either). What I found was EasyDrive app is always punishing me for bad driving practices like running red light (again, the same experience some has mentioned here with Progressive) in fear of registering a hard-brake event; and worse, slowing down excessively to turn the corners (basically, surprising the cars behind me and risking them bumping into my car) because EasyDrive thinks ONLY IF you go below 15 mph then you are doing the cornering right. I guess these EasyDrive developers (or rule makers) never drove on a real road, and found that usually 20mph is the safe way to go about turning on the right corner.
Regardless, I got 15% premium bump in the renewal despite having 110 EasyDrive score (I think Geico raised their premiums by a very high percentage in CA as well; I live in FL and have been using Geico for all the years I've been driving in the US). That pissed me off and I explored other options, and finally got Progressive for $570 for six months. The sacrifice I have to do for this lower rate is to subscribe to their Snapshot program. I used my phone and have been driving for over a month. The relief (good thing) about using Snapshot app is that it doesn't monitor your cornering score. However, like some mentioned here, it still promotes bad driving behavior like running yellow/red light in fear of hard-brakes. It also seems to be a bit proactive in determining what a hard-brake is (again, I'm using their phone app) because I registered 2 hard-brakes (the only two hard brakes that I have recorded so far in about 1.5 months of driving) on my grocery trip. I swear I didn't do any hard brakes (or maybe at most once) because I know the road pretty well and I usually do grocery runs in early mornings on weekends when there are very few cars on the road.
I know I got much cheaper ($570 vs. $710) rate from Progressive now just because I am a new customer. I am pretty sure come next or next, next renewal, they'll jack up my premiums like what Geico did, and then I'll have to switch to yet another insurer like musical chair game. I wish that the car insurers actually have a more accurate, realistic, non-intrusive tech to monitor the driving habits (e.g., the ones who don't use turn signals when turning right/left or changing lanes, which really could cause accidents) and ACTUALLY give discounts to drivers like me who are very careful with their driving (plus, my wife and I drove a total of 6050 miles in the last year). This is all to say that the risk-reward distribution system with car insurance companies is still inefficient.