Can calling a complex function inhibit $.when?
function someFunction(params) {
//Creates an object
//$.each(collection, funct() { /*do work on collection, essentially pushes items into an array */});

//JSON.stringify(results)

//$.ajax POST...this is what I want $.when to wait for

}

$.when(someFunction(params)
).then(doNextThing);

$.when(function() {someFunction(params) }
).then(doNextThing);

function someFunction(params) {
    ...
    return $.ajax(...);
}

$.when(someFunction(params)).then(doNextThing);