Really, a lot of fandoms where I like the soulbonds are the ones where there's a really obvious way in for canon. I mean I love reading the fic regardless, and often in fic, the crackier the mechanism the better - I just read #boom and it is awesome while having a deeply random soulbond mechanism - but when I think about stories I myself want to write, or where I think about ships in those terms, it's in the canons where they have canon soulbonds, or have something that's close enough for government work.

(Can I admit here that I ship Reboot Kirk/Spock as one of those deeply and inevitably broken soulbonds? Because I do.)