a.  collateral consequences (ex. still have $ damages)
b.  class actions not moot per Sosna
c.  capable of repetition, yet evading review (Roe v. Wade)
i.  the challenged action was in its duration too short to be fully
litigated to its cessation or expiration and
ii.  a rzbl expectation that the same complaining parties will be
subject to the same action again
d.  voluntary cessation by defendant (may not be permanent).