I think the most important thing about Johnson betrayals is this --
is it fun?
If your players are digging on a game where they've got to stay on their toes, watch their backs, and always be ready for their employer to turn on them (leaving them hunted by the corporation they'd pulled a job against
and their sponsor corporation), if they dig having to hole up somewhere in the Barrens or leave town to lay low for a while, if they like worrying about that sort of thing, enjoy failsafes and hidey-holes and bug-out bags and stuff, if they dig desperate firefights against ambushing corporate enemies with big budgets and big guns...and then like the occasional revenge plot? Then have it happen plenty. There are enough ways and reasons to justify it, plenty of ways to make it work in-universe, and plenty of Johnsons and companies who'd betray folks for plenty of good reasons.
If not? Then don't. If they have more fun problem-solving their way into a secure facility based upon solid, reliable, information granted to them by a temporary employer, if they prefer worrying about
the job and not
the lifestyle, then don't do it so much. There are enough ways and reasons to justify Johnsons playing it straight, and enough corporations and job types out there where it's in the Johnson's best interest to worry about
his rep, too, and to genuinely try to help 'runners get their shit done (so that he can get
his shit done). Let 'em hit it off with a semi-regular employer early on in a campaign, let them get a good working relationship going, and maybe even dangle in front of them the carrot of retainer-type long term employment or something.
Or, of course, find somewhere in between for your campaign to fall, like most of 'em invariably do. But whatever you do, remember it's a game, and is supposed to be fun above all else. So figure out what "feel" you and your buddies like, sling some dice, and go to town. Everything else is just details.
