Jon and Roger - I read your comments with great interest, thanks!
I like idea to put aikido pins in a larger context to have better perspective on why we doing it in the dojo. Other aspect of pins is that – the moment an attacker is helpless it is possible to assume immobilization. This is also a great opportunity to develop mercy and compassion which are I think some of key goals of aikido practice. Is it really possible in such sterile environment as aikido dojo, where attacker actually helps very much Nage? What conditions we need to make it actually happen?
I don't fully understand what you mean. Might be the language barrier (no offense). However, this does bring up an interesting concept, which is that "pins" don't necessarily need to be physical. (And I apologize if this thread is meant only to discuss physical pins.)
There's the story of the baby elephant chained to the tree it's whole adolescent life. Once it became an adult and freed from it's chain, it never ventured beyond a 10 foot radius of the tree. The reason being is that emotional shackles are often the hardest to break.
I've heard of freeze moves, which cause the opponent to breifly pause. And while those are more physical in nature, they don't always involve actual contact. But I'd be interested in "mental pins", wherein you use words or some other non-physical means to invade your adversary's mind and render him mentally immobile. But if that topic is beyond the scope of the thread, feel free to ignore it, lol.