I, unfortunately, was one of those suckers...
My truck didn't sell for months, thought hey, what do I have to lose? Well, turns out to be $149, $40 in notary fees (notarizing required for their "guarantee"), $7.92 in registered mail (to make sure they got it, and on time).
Not one call, emails only received a generic "someone will call you", phone messages not returned, and my guarantee being returned as the post office has determined it to be undeliverable.
On the plus side, I may have tracked down the agent who called me...so I may be making a surprise appearance at his home.
So, in summary, DO NOT USE BUYCARSNOW.CA!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!