One of the first purchased accessories I got for my PC was a surge protector back in 2006. I was 13 years old and had a much more basic knowledge of computing but understood that surge protection would help protect my PC from lightning damage, but I was wrong and it was a lesson well learned. There was a loud rumble followed by lights dimming in the house, I though this was ok because there was no surge, its just a dip, but I learned soon after that a brownout (drop of voltage in the supply) could cause much more damage than first though.
This brownout blew my power supply and damaged the 5v rail causing months of instability. It was only when I managed to borrow a PSU tester that I realised it was damaged and further research opened my eyes to what sort of damage it was.
When you get a brownout, your powers supply instantly has to draw more current from the mains causing a sudden loss in efficiency too. That also puts the components under a huge amount of stress, often to breaking points where you could end up with damaged components.
This being said, a surge protector DOES offer great protection against power surges and should still be used at all times with IT equipment.
I discovered the only way to protect against a brownout is with a device called a UPS (uninterruptible power supply) which at the time was a very expensive device. It prevents the voltage from dropping because when a UPS is installed, you have a battery between the mains supply and the computer which means if the mains supply drops completely, the battery steps in instantly to correct the voltage. It will even keep your PC running for up to 15 minutes with no electricity in the home, ideal if you ever need to backup your data in an emergency situation.
UPS devices are now available on order from Devon Tech Services from £129.99 and are easy to install.