If bandwidth is an issue, and you don't want to get into the business of developing and selling cloud services, I would suggest integrating with Dropbox natively.
On my PC I was able to move my entire database to Dropbox and then force BS to go there using a 'symlink.' This enabled me to install BS on my office computer and do the same thing. This way two separate installations are referencing the same database. I imagine this would be problematic if I had several computers referencing it simultaneously, but I am either in one place or the other. And any changes I make are mirrored on the other computer. I am pretty sure there is a Mac version of the same command but I don't use one so I don't know the specifics.
It doesn't help with the mobile app version unfortunately, as I can't trick it into looking at a different database location in my Dropbox.
So, if I currently have my default location of recipes in my drop box to use between two computers how would making this change affect that or would it?
If you want to do it on a PC, first close Beersmith. Then open the "My Documents" folder. Move, don't copy, the "BeerSmith2" folder to your Dropbox. Open a command line and type mklink /J "%UserProfile%\My Documents\BeerSmith2" "path to Dropbox\BeerSmith2". Obviously, replace the phrase 'path to Dropbox' with the actual path to your Dropbox. If it worked you will get a message saying the junction was created. When you open BS, nothing should be amiss, but it will now be reading and writing from the new location.