Safety is certainly the first time to be concerned over with any gun, but even if the take down lever breaks while firing, I don't see how anything could come off the gun. In every case of broken take down levers I know of (just 1 I personally know) and a couple dozen we've heard of here online, I think in every case the lever broke while opening the lever.
I've got over 2500 through mine now since june without any problem.
There is a issue, if it's a flawed part, a bad design, or some one over powering the thing and snapping it off is hard to say. If Ruger has a product out that has a safety flaw, I feel certain in this day and age they'd be all over a recall - that's just not the case. Liberal Lawyers would LOVE to get this sort of case.
These great guns keep shooting and shooting and those who have a broken lever send it to Ruger for a totally free fix. The 99%+ of us who never break one just shrugg and go back to shooting.
BTW - There's no added o-ring in my SR22 either.