While conducting a home inspection, we hate to see these.  This is a dryer vent that has a 14 foot rise on it.  Can you imagine a normal dryer having enough pressure to adequately blow lint through the roof?  I have seen much worse but this one is not very safe and should be checked and blown out by an expert at least once if not twice a year.  This one even had a way to take it through a wall cavity and to the exterior, which would have been much more logical.  Home inspectors should get paid more.  We save lives.