Wirelessly posted (BlackBerry: BlackBerry8530/5.0.0.1030 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)
"Non-owners insurance is mainly for persons who rent and or drive vehicles they do not own on a daily or very frequent basis."
I currently pay $60/year for a non-owned policy that provides $500K/$500K/$100K coverage. The policy also pays for rental-car loss or damage (paid out of the $100K property-damage coverage).
If I rent cars for five or more days a year (and I do) the third-party liability coverage alone pays for the coverage.
But for those whose premiums would be higher than mine, more rental days would be needed for the coverage to be worthwhile.