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Apple must have put this measure into place to stop people who use it for piracy. Currently if you log into someone elses iTunes account you can download apps that they have purchased directly onto your iPhone. I know many people who have one iTunes account per family and they all share the apps within the family. I can say that I let my brother download a poker app when he first got firmware 2.0. This is a great way to try and stop piracy but is an inconvenice for others. Personally I like to delete apps and then redownload them when I need them. Weatherbug for example, I initally got it when it was released and do not use it much so I deleted it. Last weekend when I was traveling and wanted to check the weather, I redownloaded it again for free at the airport. Hopefully this will not make it to the final realease of firmware 3.0, but I am betting that it will be included.