Indeed! I was looking at using Tahoe-LAFS in a similar manner as this dropbox feature, and happened upon a lot of information about those unpleasant surprises:

Starting from https://tahoe-lafs.org/trac/tahoe-lafs/wiki/FAQ#Q23_FUSE with links to https://plus.sandbox.google.com/108313527900507320366/posts/... and http://lists.alioth.debian.org/pipermail/freedombox-discuss/... on the subject.