I know the alarms are not exactly dependable- I set them off walking into stores because of some of my electronics...and supposedly, because of my jewelry with certain systems.
However, that alarm going off is sufficient probable cause to stop you in any jurisdiction of which I'm aware. Once they have that, they can do all kinds of things. If you refuse a search, for instance, they (usually) will contact the police, who will arrest you if you don't consent to a search...and then they can search you incident to the arrest.
I know of no case in which a laywer has successfully argued otherwise, except in those cases when management knew that the alarm was malfunctioning, and that doesn't mean giving the occasional false alarm, I mean going off for all kinds of reasons (like birds, a stiff wind, funky jewelry, etc.) and still depending on it.
The justified use of force comes in not when the alarm goes off, but when you refuse to be cooperative with a simple request of proof of your purchases and attempt to leave the premises, and is limited to that which is reasonably required to detain you. It cannot escalate to deadly force unless and until you escalate the situation to that level or present an obvious threat to use deadly force yourself (for instance, if what you were suspected of stealing was the gun that now resides in your jacket pocket).
There are other anti-shoplifting measures out there- for a while, exploding security tags, expecially those with dyes, were popular. They made the merchandise unusable and often marked the shoplifter.
Unfortunately, they were quite bulky, and if some clerk forgets to take it off...POW! And that happened enough times to make some retailers quite leery of them (something about honest people getting burns, dye, and plastic shrapnel being bad for the public image).
Visual monitors are quite effective- just ask someone working security in Las Vegas. But they are only as effective as the people doing the monitoring, and that costs money. And really, visual monitor systems only provide descriptions to police as opposed to prevention.
Ultimately, the cheap, non-explosive, easily concealed beeper tags won out.
If they are wrong, their responsibility depends upon the totality of the circumstances.
If you showed them your merch and receipt, then released you, its kind of no harm, no foul. Depending on the timeline, you may still have to talk to the police, but that is highly unlikely.
If you showed them your merch and receipt and they still detain you; if you were stopped because of profiling; if its revealed that they had no probable cause (they knew the alarm was defective) and so forth- you have a civil case at least, and possibly a criminal one.