To answer the OP, if you're, clumsy and/or incautious/ and or careless and/or reckless, you might well consider buying a service agreement on a sophisticated piece of portable electro/mechanical/optical equipment that may be frequently subjected to risky situations and environments. On the other hand, if you exhibit the care and caution most photographers do with their equipment (especially those who frequent this forum), you'd probably waste your money.
Generally speaking, these service agreements were conceived by the marketing devils 20 or 30 years ago when the quality of consumer goods took a turn for the better. Solid-state circuitry, improved manufacturing processes, etc. all pointed to much improved reliability and endurance. They also knew if failure would occur, it would typically happen early (first month or so) when warranty provided replacement anyway. So, they decided to go into the insurance business, always a profitable venture. Buying the service agreement is simply betting against yourself, and the financial backers on these bets have been raking in money for years -- even better than gambling casinos!
Finally, an old story from personal experience. About 25 years ago, when these service agreements were just being introduced, I bought a stereo system from Circuit City (about $1000). While closing the deal the congenial sales guy asked if I'd like to purchase the "extended warranty." I told him, "No, I already have an extended warranty. If this thing stops working in the next year or two, I come back here and beat the hell out of you."
Well, he became somewhat less than congenial and was happy to quickly help me to the car with my purchase. I went on my way with a smile.
