i often worry about this but it's not enough to keep me from riding. my bikes are in the $1500 range. the racks always say "use at your own risk" but the truth is that if the bus driver is at fault it's likely that you could settle with the transit agency - especially if you're on the bus when the accident occurred and you're not injured. the transit agency i work at would be happy to settle some of it's suits for $1500. worst case scenario i could probably pull components off the old bike and re-use them for a significant savings.

we typically have one accident per 1,000,000 miles operated, and most of those accidents are mirror strikes. i can think of 3 accidents we've had in the past 3 years that would've damaged a bike on a bus rack. not a huge risk.