Upon launching Cydia, you can see the new Manage Account option
Cydia recently added a new feature called Manage Account. It's purpose is to let users easily see and install packages they have already purchased. Know that this only keeps track of packages that are purchased through Cydia's payment system. Those apps that use their own payment system won't show up.
Those applications purchased through Cydia will be linked to your Google or Facebook account so long as you connect and login.
Later, if you buy a new phone, or if you must restore your firmware, rather than lose your purchases or have to pay for them again, you use your login to authenticate your previous purchases. The image below is a screenshot of the new feature:
As shown above, the items will be tied to your Google or your Facebook account. It's a great new addition to Cydia, especially for those who want to upgrade their phone but may worry about losing applications they've paid for.
It's also one step closer to the more polished experience you have when going to Apple's App Store, for which it has always been nice to have a feature that let you keep your purchased Apps after buying a new device.