while its easy to complain, but there are practical issues either way:

1) Dev bans accounts with shared ip- you would exclude all those that played from public computers (work, uni etc, serious loss of income for evony), and you would breed a new type of multi-accounts from people who uses 3rd party proxies or can reroute connection through multiple in-house ip (i.e. if u are a network admin playing at work). anyway, the incentive to enforce this rule and chance of sucess is small from dev point of view.

2) Dev say its ok to do multi-accounts- that would make player feel obilge to create more accounts, only to abandon them later, creating a vast number of dead cities across the map. surely thats not right?

I think leaving it grey is the best option. unless they can enforce it fairly without discrimination.

anyway, look at it this way. Looking after 10 cities and keeping a massive army feed is already a full time effort. Whoever have full-strength mutli-accounts must have really suffered in real life. gaining an upperhand on a primitive game like evony is of little consolation.