I highly recommend the Sprint PCS equipment replacement insurance program. I think the fee is something like $5/mo. I used to have it until they kicked me out of it (heh) for submitting 2 claims in a 1 year period.
Basically, you enroll in the insurance. if your phone is lost or stolen, you simply fell out a police report, then call the insurance line (after suspending service, of course) and submit your claim. Within a few days, they will ship out a replacement unit (could be refurb or new -- their choice) to you. In one case, I was at a party (no big thing, just a small get together of friends, including kids, at my sister's former daycare provider) and sometime during the party, i realized my phone was gone. i tried calling it several times and never heard it ring. Checked all over that place as well as my car and sister's house, but it never turned up. Called the police and made a claim. Phone was shipped and I wasback to normal in a few days. The 2nd time, approximately 5 months later, i went through a security metal detector at work and placed the phone in the tray with keys and stuff. Apparently, i forgot to pick it back up and put it on my belt. It was a friday, and i didn't realize it until i got home. i made a couple of phone calls, but security didn't have any record of it. Checked again on monday, and was told someone had picked the exact model the day before. Contacted that employee, and he said he didn't have the wrong phone. Made a claim, waited a few days, and got another replacement. I had to pay thre $35 deductible each time, but i had a Motorola StarTac and it was still retailing for close to $200. About a week after i was back up and running, i got a phone call from a Sprint store telling me they had my lost phone. i went and picked it up, but it wasn't activated anymore, of course. Decided i could fight to have the old one reactivated and the new one sent back to get my $35 credit, but then decided I might as well keep it for the extra battery. They charged more than $35 for a new battery, so I came out ahead, although i didn't purposely do that. (although that would probably work if you wanted to be fraudulent about it) Anyway, I saved myself a lot of money by having that. I've now kept that last phone for about 14 months without losing it, so I'm doing well. (knock on wood)
if you bought a cheap phone (sub-$100) phone, maybe it's not worth it to you, but if you have a newer model phone, especially an expensive one, I highly recommend it just to protect your investment.