racks have a weight limit.

Xtracycle
&
Big Dummy

are legal to carry passengers.
the Dummy has built in foot rests
and/or
XtraCycle sells "footsies"

from a litigious view point...
if a person was to get hurt, and need medical attention
insurance is going to want to know the cause, etc...
if its something significant and the cops/ambulance shows up, a police report, etc...

you get the picture...

someone will get sued, bcz someone will have to pay the bill.
(at least that's typically how things like this play out in California)