In all seriousness though, a lot of the reason the OP listed to not jailbreak don't really apply anymore.
1.) It's not illegal although it will void the warranty if they find out. I restored my jailbroken phone the other day and had it replaced.
2.) At the making of this thread there only existed the iPhone 2G and 3G. Both ran off of 128MB's of RAM. I'm not surprised they had performance issues, the iPhone 4 runs off of 512 and even the iPhone 3GS functions much more smoothly with 256.
3.) Wanted the latest firmware is a valid reason to not jailbreak. Although to be honest I don't think it's very worth it unless they released a major revision.
4.) You don't necessarily have to reinstall all of your Cydia apps and whatnot. There do exists apps to back all of that up.
5.) I'm not sure if this is a really valid reason on the OP's part or still applies with the newer iPhones. I've personally never really had issues with performance but I'll admit I never jailbroken until the 3GS.
6.) It looks like themes have advanced a lot since the time of this threads creation. All of the stock apps are modified by my theme but I do have plenty of apps from the App store that aren't. I just leave those in folders anyways.
7.) I'll never tire of using BiteSMS, activator, MyWi, Fakeclockup and Safari download manager.
8.) Err, I could live without SBsettings. Kind of silly to assume that everyone jailbroken automatically uses it though. It's somewhat useful for when I need to disable Wifi or enable MiWi.
9.) Maybe back then but honestly, this no longer applies.
10.) Me.com > Login > Find my iPhone > Wipe