How dangerous is a very out-of-true disc brake wheel? While walking to work this morning my eye was caught by an odd movement on a bike passing me several metres away.  The front wheel was far from true laterally, though it didn't look out of round.  It was on a basic hardtail/hybrid with front suspension with disc brakes; it was fairly close but not rubbing on the rather wide forks.

If we assume that this wasn't due to impact causing weakening I couldn't see, how dangerous is it likely to be?
Another danger of riding an out-of-true wheel is cornering.  When on the straight, the wheel may be "round" while wobbling from side to side.  

But when leaning into a corner, the bike is no longer vertical, so that out-of-true in the rim is translating to an out-of-round as well.  So the wheel of the bike will be rising and falling ( "oscillating" ?) sideways at roughly twice the wheel's RPM.

Effectively that could make the wheel loose traction much easier on the faster corners, or even at moderate speeds if the corner has any treacherous features like dampness, dust, sand, gravel, or even painted lines.