[quote=Elayne]
So both our shades are not a big fan of the people who summoned them and I was wondering what exactly makes any shade serve the necromancer as opposed to running away?
[/quote]

Shades aren't summoned to the necromancer, they're more of collateral damage and just punted back to the world of the living wherever. Basically, when the Necromancer passes through the second gate (Scorpion) a soul is hurled out so they can continue on; in the Necromancy hider I assume that's the ghastly scream of a woman. The souls carried back by Necromancers aren't Shades, but something else entirely. 

And Adune is neutral towards the necromancer that brought him back. Depending on the exact nature of them, he might have even ignored them a few years ago.