The idea is that you are using a spare key to begin with. If you lose the original, you are screwed. At least keeping the original key safe at home, you can have someone besides a dealer make you a new key. Heck, once you have two keys, you can buy the blanks online for ~$10 each and program them yourself at home.

Adding a remote start? Spend $10 and make a key specifically for it. I've got two spares plus my original, but once I add my remote start here in a bit, I'll be getting a new key specifically for the system. Again, I'd rather spend the extra $10 now than have a $150 bill later.

 

I only have one key for my PT cruiser, so I took my own advice and did what I mentioned above. It did not work. No matter how close I held the transponder key to the position it would be in, the car would start then shut back down.