I think it is important that we have an agreed upon definition of mobility and flexibility.
Flexibility is often lumped in with mobility, just as strength is often lumped in with stability.
Flexibility: the ability to elongate a muscle, such as when the hamstrings are stretched during a forward bend.
Mobility: A broader concept, involving the muscle(s) and joint(s). It is a more inclusive term when considering movement.
These definitions are widely accepted in physical medicine, and I think are appropriate to support the discussion here. Therefore,
ETinCYQX was more correct in his statement that Yoga is more mobility based, because the poses are meant to put multiple joints and muscles through a range of motion than mere static stretching of a single muscle group.
Strength: The ability to produce force or movement.
Stability: the ability to control force or movement.
In most cases, stability is a precursor to strength.
Gray Cook MPT and Mike Boyle CSCS both are experts in this field. Here is an interesting approach to thinking about these concepts from a Joint by Joint perspective of the body:
http://graycookmovement.com/?p=118
and a follow up:
http://graycookmovement.com/?p=119