"YAGNI" is... in general... not that useful when used by people who've never worked on a particular type of project, because, almost by definition, they don't what what they will and won't need.

And... defining "needs" is its own set of headache. Needed by who? I'll tell you what, we need to ensure we have a logging system in place that can alert folks, and we'll need the ability to view logs in production, and share access to those. Years ago I got "YAGNI" back on that, and months later... weird bugs that no one could reproduce, and the minimal logging in place was only accessible by one guy who was out of town for a week. But hey... we got those "rounded corners" to work in IE5 and IE6 with only an extra week of work - yay...

YAGNI is a good principle, but as with most ideas, you get problems when you introduce various types of people in to the mix. Someone who's never done a project type X should not be the one making YAGNI decisions when other people on the team have done multiple "project type X" before, and are trying to introduce basic requirements.