Re: "but... but... but... it's almost free!" "Nah, we're good."
"If Linkedin can't use Azure at steeply discounted / possibly free pricing, then what does that say to anyone else considering using Azure?"
It was stated that Microsoft does NOT give discounts to other Microsoft companies and they must pay full retail prices for Azure.
So your one assumption you based your whole comment on isn't valid, ie they'd get such cheap hosting it doesn't make sense not to do it.
And remember, LinkedIn was created in 2002 and went public in 2003 and Azure first showed up FIVE years later. AWS was launched in 2006 so just maybe LinkedIn developers built their platform to scale off a clustering technology which is close to the metal and doesn't work well or at all in the virtualized environment cloud environments which came years later.