Do you have data on reddit's downtime to backup your claim? https://twitter.com/redditstatus shows the last downtime was on April 9th, and that was scheduled.
I don't think this necessarily means Reddit has crappy engineering. It could be they've just realized that 99.9999% success at serving pages is not a worthwhile goal. I mean, it's Reddit, it's not air traffic control — nobody's going to be hurt if they have to wait 90 seconds to see random crap on Reddit.
http://www.reddit.com/r/announcements/comments/2hyyhu/when_t...
From 5 days ago and last night, respectively. alienth disowns the threads after the downtime is complete so there's no solid record I can refer to (these are just posts I happened to be around for).