Forget dropbox.
copy.com
I've posted this before.
My clients all give me internal email addresses for convenience. That means I need multiple dropbox accounts.
Copy let's you link all of your email accounts to one copy account so no signing in and out when a different client sends me a link to something.
Equitable sharing. With dropbox if someone shares 5 gb with you it counts as 5 gb in both theirs and your account. With copy the same 5 gb only uses 2.5 from each account. The amount of data is divided by the users so even if 5 people share that same 5 gb it only counts as 1 gb in each account. Put another way the 5 gb is 5 gb not 5 or 10 or 25.
Currently they are still giving credits for driving users. I've got 60 gb for free right now.
Use my referral link and we both get an extra 5 gb for free.
https://copy.com?r=BgtGZC
I still stand by FB as the solution. A benefit for FB is she can comment, have dialog on specific items posted and will get notification of new content. Besides, it's dead simple.