there are 2 seperate situations:
1. your bike gets stolen and you make a claim against a renters/homeowners policy. Some policies will have a statement saying you can only get "actual" cash value. So a 1982 Univega is worth very little. Example is your friend whose bike got ripped off. He signed a contract that he is locked into & has no choice.
2. a driver hits you and you make a claim against the driver's car insurance. In this case the claims adjustor may say they will pay your "actual" value, but the truth is this is up to adjustor. If you disagree you can deny their offer and take them to court (which is the risk) for full replacement. You never signed a contract with the other driver's insurance co so why would you agree to anything less than replacement value?
This is really simplified. I have a special rider on my renters that allows for full replacement value and it didn't increase the cost by much (compared to my not so good chicago zip code).
Hopefully that cleared up my point.
jeff