Update didn't backup iPhone? Various questions

My upgrade to iOS4 on my 3GS went super smoothly. Once the update was downloaded in iTunes, the update took no more than 10 mins, which was quite surprising.

However, I thought the update would involve a backup of my iPhone. iTunes appears not to have backed up my iPhone. Did anyone else experience this? Is it possibly because I manually backed up the phone about an hour ago?

All of my stuff is still on the phone, though iTunes told me to authorize this computer and transfer my purchased items to iTunes before the update (weird b/c I haven't bought a single app. All of mine are free.) Why did iTunes have me do this if I haven't purchased anything through the app store? Just curious here.

Furthermore, I know have backed up my iPhone before, but when I go to preferences and look at my backups, I only see one. Do backups get deleted when you update iTunes?

Thanks

 

Ahh I see. But what's the point of transferring them to iTunes before the update? Wouldn't they all transfer over regardless?