MB's, GB's, TB's.. But, how many??

Storage drives are getting significantly cheaper. So cheaper, in fact that people have started buying 1 TB hard drive instead of a 750 GB one. Cheap storage space is not everything. You have to consider the speed of the system as well.
While buying an internal hard drive, people often forget that a larger hard drive means a slower system. And also, more number of hard drives mean a slower system as well.
And if disaster strikes and your hard drive crashes, you lose more amount of data than you would have, had you would have had a smaller one.

Research says that as the years have progressed, hard drives have become cheaper while their reliability has plummeted considerably, especially for larger capacity hard drives.
In daily life too, you'll see 500 GB and 1 TB ones crashing more frequently than their corresponding 320 or 750 GB ones.
So the question arises, how do we choose a good HDD with ample space. Well that's extremely simple, keeping a few points in mind.
When calculating storage space requirement, do not keep more than 35 GB reserved for your system partition containing your operating system and your basic everyday applications. Add in an appropriate size for your productivity apps like adobe suites, autodesk products, etc etc.
After that do not start counting your pictures, documents, music and videos. Remember that you can save your pictures and videos to an external hard drive or the cloud for more reliable and efficient storage. Just keep the important ones on the system itself. Plus add a couple of 100 GB if you are a gamer.
But that's it, no one needs more storage than that, and there is no need to install a hard drive that's gigantic.