I would also love official support for 4shared.
Thanks in advance.
I'm interested too.
Paid accounts for ADrive and 4Shared can be used via webDav, but free accounts cannot. New customers get a short trial of "premium server", so they could just connect to slower services to backup their data before the end of this period.
But please, do what you can to use their web api to let even free users connect to these services.