I've been were you are at dozens of times. Some people just can't be trusted. It's not always like that though. But there are usually signs, even small, that you sub-consciously notice. However deep the emotional wound, you'll have to get past it and move on.
I always notice, that in most scenarios, there is a magical/chemistry that's needed, and when one part of it is gone, things go south pretty quickly for the other side. I wouldn't dwell too much into the betrayal aspect, otherwise you'll never get over it and might miss a great opportunity. It's a lot better to come to new 'opportunities' with a jaded mentality, rather then simply refused to partner up - that way you know what to look for the next time around.
I can honestly say, I wouldn't be were I'm at without all the healed stab wounds in my back. I've gotten used to it so much, I engaged my mercenary mind of just get the cash. The last backstabbing I was literally yawning in the board meetings, I even started trolling them playing the ignorant fool. They thought I cared about some intellectual property for some source code. They didn't want it out there - had me sign a contract to get the agreed upon "get the fuck out of here money". Even were talking shit back and forth in emails about the plan and backstabbing - not realized I'm root. LOL Once the wire cleared, I send them the URL to wordpress.org and the open source plugins I used. LOL. A couple months later one of the other major partners left the operation, and now I'm getting phone calls from the gang asking what's up and wanting to work with me again. They're still pissed though, said I duped them as they tried to backstab me, I still chuckle when thinking about that shit. I saw it coming from a mile away, and was already out the door. LOL. The first backstabbing though weren't that fun or funny. I still feel the betrayal sometimes. I was a young and bright eyed kid. Shit happens.
Projects fail, businesses fail, but as long as the fire from within you doesn't die cause of a bad experience, you'll be better from it. Past wounds can cripple your future prospects. Like the advice given, always stay paranoid, but move past the pain. I know all my former biz partners and the projects I left are either completely out of business or aren't doing as great as when I used to be there. It's kinda of my own evil pleasure, watching them fail once they realized how good they had it when they wanted to start fucking around. I'm still here, and they're not.
With each ending, comes a brand new beginning, perspective, and opportunities. Use the experience to tread more carefully who you go into business with, and to make sure you have control in place to never put yourself in that same situation.
Also, DON'T EVER DO BUSINESS WITH FAMILY OR FRIENDS!
"In the Kamigata area, they have a sort of tiered lunchbox they use for a single day when flower viewing. Upon returning, they throw them away, trampling them underfoot. The ending is important in all things." - Yamamoto Tsunetomo (Hagakure, circa 1709)