Local officials recently confiscated the controversial breast milk ice cream served at London ice cream shop, Icecreamists. Perhaps it was because of this obvious breast milk no-no. 
From page 288 of the Vitamix Whole Foods Recipes cookbook:
Only use freshly-expressed breast milk -- never use frozen breast milk that has been thawed.
Ah, now you know. (and also know breast milk is "expressed"?)
[youtube http://www.youtube.com/watch?v=V_n1zoU8G_M?wmode=transparent]