The idea is to create a smartphone that is completely modular, so each component - display, CPU/GPU, battery, storage, camera, Wi-Fi, Bluetooth, etc - are all separated into discrete blocks that all attach to a main board and are secured by just a couple of screws. This design would allow for easy repairs, because you could simply replace the broken component instead of replacing the entire device, and it would offer tons of customization. You would truly be able to build your own smartphone.
It's a very compelling idea. Of course, it would need a lot of support to get going, because it would require hardware manufacturers to build blocks rather than building complete smartphones; and, in general, companies don't like to change business models that are working well for them. The Phonebloks team isn't looking for monetary support right now, just social support. They are asking for people to support the Thunderclap page, and on October 29th the social blast will go out.
The project wasn't planned to launch on Thunderclap until next Monday, but the idea leaked and has gotten big already. The original goal was 500 supporters, which was reached in a few hours. We're still not 24 hours into the campaign, and it has already upped the target to 10,000 supporters. As of this writing has attracted over 21,000 supporters, and there is still over 1 month to go.
source: Phoneblocks (Thunderclap)