Have you ever run their pages through css/html/xhtml validators? Ouch. Their homepage just got flagged for 50 errors by the w3.org validator including gems like still using VALIGN in a table tag and other deprecated tags such as CENTER. CENTER! I haven't used a CENTER tag since about 2002 and I winced while doing it.
I use the FF extension Page Speed and the only thing preventing me getting a 95+ score are the snippets of code from google themselves. If I remove adsense and G analytics, my pages get 96. With them, they get scores in the 84-88 range.
And remember, this is the company that is now going to start penalising US for page speed. Do they penalise for coding validation? They harp on about it so much. Why don't they follow their own play book?
do as I say, not as I do.