Sure, if you do this the naive way (map files onto the git repo 1:1).
I don't know how this project is doing it, but adding a buffering/sharding layer for large files would alleviate this problem at the cost of worse delta compression (among other things).
That said, I still don't think git is necessarily the best platform to base a Dropbox alternative upon, but the commit resource hogging is very fixable.
It's unclear to me how buffering/sharding could fix this? The bytes still need to get into the repo. That's still expensive and time consuming even if it is chunked or asynchronous.
Look at bup a backup system based on git. They face simular problems. I was at a talk by one of the developers. Very intressting and very technical about how they solve some of the problems, spezally about large files.
I don't know how this project is doing it, but adding a buffering/sharding layer for large files would alleviate this problem at the cost of worse delta compression (among other things).
That said, I still don't think git is necessarily the best platform to base a Dropbox alternative upon, but the commit resource hogging is very fixable.