Problems

An IPv6 scoped address does not provide sufficient information on a scope boundary.
"ping fe80::1" would confuse the ping program if you have 2 links
       ??                    ??
      <---  +--------------+ --->
    --------|"ping fe80::1"|-------
     linkA  +--------------+ linkB

an identifier of the link should be provided to the program
same kind of problems arise in site-local addresses
It's hard to reuse scoped addresses using "cut and pase".
e.g: lookup a routing table and telnet to a gateway
a link-local gateway can't be "cut and pasted" without a link ID