GPU and MCP and CPU are some of the main chipsets on your logic-board. These chipsets have a lot of number of pins underneath. They are simply the brain and heart of the logic-board. If any of these chipsets fail, you experience some major issues with your device.

What could damage these chipsets?
1) Over Heating
2) Liquid and Corrosion
3) Manufacturing

-Overheating could cause the balls under these chipsets to melt and connect to each other. This could easily stop the chipset to work and in some cases could also damage other components on your logic-board.

-Liquid and Corrosion can also make the balls connect to each other.
-And as much as some companies do not want to admit, manufacturing these chipsets could cause major issues.
The famous A1286 model 2011 Macbook pro 15″ came out with a lot of complaints about graphic issues. You can simply read about this issue online and see how many customers were not satisfied and were hoping for a recall on these devices.

If you experience GPU problems, you may see your screen pixeling out in some areas. Your system not being able to boot up. Freezing on the apple logo, and only booting in safe mode.
This is a major issue and very expensive to fix. The repair involves 3 steps.
1)Reflow
2)Reballing
3)Replacement

It is very important to get warranty on such repairs. Check out some of the Macbook Repair Stores in Toronto for their warranty and type of service on this subject.