Sometimes, betrayal is unintentional and [seemingly] unavoidable. I experienced this in a match recently where I had several units in a far off place slated to capture some islands that had been occupied by another player. I had since negotiated a peace and alliance offer before my war actually started. But those other units were forgotten and eventually reached their destination. The other player was absolutely convinced that I had betrayed him, and he didn't believe me when I said it was unintentional.
Sometimes the betrayal is due to misconstrued words in a message. In another match, I was seemingly betrayed when my so-called 'ally' sent a message to my other ally threatening them if they didn't cooperate with him just the way he wanted. He said that if we (his allies) got in his way of taking resources from our third party enemy, that he'd just attack us and take the province(s) anyway. Now, supposedly, he only meant that to my other ally -- who was in a weak position at the time -- and was bullying him. But the way he wrote it seemed to mean any of his allies who gets in his way would be trounced.
Well, my other ally forwarded that message to me (certified unedited) and I had tangible proof that we were being used and potentially threatened by our principal ally. The other ally had told me on numerous occasions how he was being threatened by the first ally, but I had dismissed it as misinterpretations or over-reactions. Well, once I saw this proof, I knew immediately that the first ally was intimidating my other ally but hadn't been doing so with me as I was more of a match against him. At this, I decided that I would not allow myself to be manipulated into eventually cornering myself in the late stage of the game and then losing to that a$$hole.
I forwarded the message to the first ally, and asked him to explain himself. He claimed it didn't mean what it clearly stated but he didn't deny authoring it. So, with my other ally in hand, we canceled our alliance with him and went to war with him.
Boy, did he get pissed. He accused me of back-stabbing him. Of course he ranted and raved and wrote scathing articles in the newspaper (to which I eloquently responded only to be called a 'silver-tongued devil'). In numerous posts to me and to the paper, he practically called me everything but white. He then accused me of multi-accounting to which I accused him of the same. Finally, he tried to 'report me' as if I had done something wrong.
Last I've heard, he's been kicked from the forums (I suspect he may have ranted all over himself here and got banned because of it). Of course, the game went on without him but not before I called on yet another ally to assist in taking him down. United, we did exactly that and he went down very loudly kicking and screaming into his own abyss.
With his reaction, which was fueled with much anger and expletives and rants, I accept that he may have really believed that he was the victim. But I am a player with integrity and I judged his excuses to be nothing more than the ravings of a lunatic. I'm glad to see him gone and I do not accept that I ever betrayed him. I don't know if he's been banned from playing, but I suspect that if here were, he'd just find another way to get back on with a new name and continue his selfish playing tactics.

It seemed like such a waste to destroy an entire battle station just to eliminate one man. But Charlie knew that it was the only way to ensure the absolute and total destruction of Quasi-duck, once and for all.
The saying, "beating them into submission until payday", is just golden...pun intended.
R.I.P. Snickers <3