Jeff,
I think you can manually synch using the export/import and merge commands. I suppose it would be possible to synch automatically by having BeerSmith Import and Merge at startup assuming you have a shared network drive between the two computers and the location of the other system is known. I'll look into it to see how hard it might be.
I've also been toying with a recipe repository available via the internet, though this is a pretty big project.
Cheers!
Brad