Use git-submodule for your sounds and videos and other binary blobs.
Unity makes their own asset server for people who aren't comfortable with git or svn -- there's plenty of debate on the quality of this option, and it's more money, but it's definitely cheaper than losing your entire game.
And you often have more than one change at a time.
As for two gigabytes not being much I don't think their repos is that small. Most of us would properly have no issue downloading it, but you have to upload them (and DSL isn't symetric) and you have to find some place that is willing to host those gigantic repositories.
Or use an external HD, which are a bit faster and also bigger.
Though SD cards are nearly indestructible, you can drop em or drive your car over them, the one in my camera even survived my house burning down, so yeah.
A bunch of friends and I wrote a rather simple game in Unity3D and our repos went to become more than 2GB.
It is not the code which isn't usually that large but you have to consider the assets, especially images (3D models usually aren't that bad, but they can still run up in a couple of MB), sound and (if you are unlucky) uncompressed video.
At too it that the binary assets can't really be stored in a version control system except as snapshots and you can see the problem.