Having worked at a couple, I think I wouldn't be too far off to say all of them.

I still remember a week into the first job fresh-from-college me marching into the VPs office to tell him the source code was terrible and they were only still running due to luck. It was not well received (or right)

I almost did the same thing. But then calmed down and said maybe I have no idea what I'm talking about. I was right. I had no idea what I was talking about.

Users dont care what your code looks like,Early Facebook code was no better and look where they are now... it's about the product. Wordpress is a piece of shit from an engineering perspective yet it's the first blog engine in the world. Because its features are not that bad.

Things are different today though,people tend to use native apps, users want realtime features,hard to do that in pure PHP and scale.You often need 3rd party techs,mostly java based...

>I think this just goes to show that you can have a lot of popularity even if your code is just sorta glued together.

As if OpenSSL didn't prove this already.

imgur might be a candidate.

I doubt it. At their scale (a million uploads daily, three billion monthly pageviews), crappy code is unlikely.