Thanks for the detail! My personal experience is generally in strategy 1 as you outlined, especially in being that lead person. I know a lot of people like the appeal of strategy 2 (myself included) but like you mentioned, there's a number of ways that critical code can fall through the cracks. It's great for a general "good work, I like the way you did that" or "what about doing it like this" kind of review but beyond that doesn't provide many safeguards. That being said, I've heard a number of complaints about the organizational/cultural aspect of strategy 1.

In full disclosure, part of the reason I'm asking is to do some research for a product of mine: https://pullapprove.com. Currently I feel as though it serves as a fairly flexible platform that can accommodate either (or both) of the strategies in various ways, and just want to make sure things are headed in the right direction. As you mentioned, the process for choosing reviewers could be handled several different ways and I wonder if there's room for some tools to assist in that. An interesting one to me (which PullApprove doesn't yet support) is automatically choosing reviewers based on git blame information (https://github.com/facebook/mention-bot) -- which could get at your last point.

I feel like there's a ton of value in doing code review that, I personally, drastically underestimated for a long time. I'm interested to hear more about the kinds of problems different groups have with code review and trying to figure out if/where/how a tool like PullApprove can alleviate some of the pain and make it an easier process to adopt.