“I’m going to erase my G1 phone, can I download the apps I bought or will I need to buy them again?”
You will not have to buy apps you’ve already purchased, all you need to do is download them onto the phone again.
How to re-download Android apps:
1. From your Android phone, head over to the Android Market.
2. Tap the Menu button, and then tap Downloads.
3. Here is where you can view all the applications that were downloaded and “Purchased”.
4. Choose the app to download and install as usual. You will not need to pay for the app again, the download should be free.