Many users use SSD disks (and I believe many more in the future) for their OS. 128GB SSD disks are common place nowadays and many users (like me) use their SSD for dual booting (Windows and Ubuntu). Ubuntu installations like this occupies 20-40 GB (/ , /home and swap). Up to now there was no problem. In a few weeks though, triple A games are coming to Ubuntu (i.e. l4d2) that require probably tens of GB for installation.

In windows there is no problem, because you can install a game anywhere you want (i.e. I install games in D:/Games/). In Ubuntu, though, programs install files in many places (i.e. /usr/* , /lib, /etc ) so from what I remember, I never had the option to choose where to install a program.

So, how will it be possible to install AAA games that require many GBs, when our Ubuntu installations won't have the necessary space? Could a /opt mounted on a mechanical disk (HDD) be the solution? Is it something I am missing?