If it is a Factory Warranty it is Not a Scam...Beware of others off brands however. I currently have on on My Suburban and HHR that is a True Bumper to Bumper everything covered including normal maintenance and wear and tear items, used many times for small things and it is a 0$ deductible.
In todays economy, I make good money but still a $400 repair bill takes a huge chunk outta my Golf and Steak eating....lol
Some of the good ones, use the rule of 78's on a refund if you trade or sell or total the car or truck and you get a portion refunded to you.
Some of the bad ones said if you never use it you get a full refund...they are outta business. HMMMMM!
Investigate and compare and do some shopping, cheaper is not always better.
They are well worth the investment, and as a Long time GM for a chevy dealer, when i used to appraise cars I would give a higher trade value to one with a warranty, because all problems usually got fixed right away instead of procrastinating and having that problem effect something else.
But the decision is always yours not mine...