The bottom line, though, is that you should never take ukemi unnecessarily. If you don't feel that you should move, then don't move. Usually, doing this will at least gain you some insight into the reasons why you should or should not have been moving.
As a real seeker in the softer sides of AiKiDo (as well of some of the harder sides), I really really agree with this. One of the nice things about a 'softer' school is that you know they're not likely to break your arm if you don't fall down for them.
I more often find myself taking 'unnecessary' ukemi for people who I worry might accidentally break part of me than for people who are too gentle with me. I worry about this when I am visiting some dojos, just like Jason discussed worrying about his own uke in the opposite situation. I think my interpretation of this is that I'm still exploring all the possibilities of what being uke can mean.
As far as hard and soft and blending and throwing, I have two thoughts. One is a common seidokan teaching and the other is my own:
In seidokan we often said that when AiKiDo is done properly, uke should feel like they stumbled and fell rather than that they were thrown.
I often tell people when I'm teaching that if uke isn't already falling, it's very hard to MAKE them fall. On the other hand, if they are already falling, then it isn't necessary to MAKE them fall. You just have to let them fall.
In my experience, most of AiKiDo study is about realizing that it is you who is preventing uke from falling and learning how to get out of their way.