Is the ISP of your server same as that as your residential broadband?
It may cause problem if the ISP of the user is not the same as that of the DNS resolver.
Some connections(e.g. akamai, some other CDN providers, some other ICP providers like Google) may be less efficient because some ICP have IPs from each ISP and answer DNS queries with the IPs in the corresponding ISPs.
In my case, Facebook still works well but with high ping.