This command worked in previous versions of 1.8:

/effect @p[team=!herobrine,r=255] 4 10 10 true

Where mining fatigue was applied to everyone who was not a member of team "herobrine". As of the 1.8-pre1 update, this command gives the following error:

[23:58:27] The entity UUID provided is in an invalid format

I've tried all different configurations and variants of the command, but this works:

/effect @p[team=herobrine] 3

and this does not work:

/effect @p[team=!herobrine] 3

Any exclusion fails. I tried with "name=!ogradyjd" and that failed as well. Tried same selector with /msg and /gamemode and both succeeded, so this seems to only affect the /effect command.