By personal use I have a few terabytes used in storage by experience it is distributed like this Movies and series A blu-ray movie rip might get to 4 GB each. Aplete series can take up several hundreds. Games video games now are using absurdly big amounts of storage. Quantum break uses about 8GB The Witcher III uses around 5GB. I own about 1 games they alone use about 1T. Images and video from Mobile With today mobile cameras you can get very good pictures at the expense of high storage use say 731MB per photo. I backed up my phone yesterday and I had 5 photos all in high quality PLUS videos which were about 1 GB each (18p 6fps). Music Of course music! Even with the streaming services a lot of people is morefortable having their music on their own devices. Specially with the newest standards which have richer (and larger) media. After a few years of storing music you can get obscene amounts of storage used for that (last time I check I had around 1TB also). Backups For tech based careers you will have several software installers beta software own developed software and the databases for them (a DB buckup can fairly easy go into terabytes size). I think those are the main suspects.