sure - totally agree re: passwords/unsubscribe/etc. I'm not saying LinkedIn has the best product or user experience or retention/engagement - but they have done a great job growing the userbase.
as for flakey - maybe you're smarter than most of the Growth Hacker Conference attendees :) when Elliot surveyed the audience about which channel they'd focus their time/effort on, the vast majority chose the channel with the lowest conversion rate (i'm assuming they thought it had the most potential upside?) - which is exactly the opposite approach that Elliot took (focus on what's working, let engaged users do the work, reduce engaged user friction), and what actually allowed them to grow.
as for flakey - maybe you're smarter than most of the Growth Hacker Conference attendees :) when Elliot surveyed the audience about which channel they'd focus their time/effort on, the vast majority chose the channel with the lowest conversion rate (i'm assuming they thought it had the most potential upside?) - which is exactly the opposite approach that Elliot took (focus on what's working, let engaged users do the work, reduce engaged user friction), and what actually allowed them to grow.