Considering Chrome's market share, it's enough for Chrome to break something to force server-side action. Distrusting Symantec certificates is a prime example,

Considering Chrome's market share, it's enough for Chrome to break something to force server-side action. Distrusting Symantec certificates is a prime example, I think. The breakage rate for distrusting all Symantec certificates is significantly higher than 0.1%, but there is just one vendor that needs to fix things. Middleboxes are considerably more problematic, since you've got a lot of manufacturers out there, some of them might actually be out of business. Pushing firmware upgrades to all of those middleboxes would also be a nightmare. And the icing on the cake is actually finding the malfunctioning middleboxes, since they can be anywhere between the end user and the web server.