Consider a website where users can post house advertisements for free. Obviously, there should generally be one ad per address. If someone tries to create a duplicate for an address, then they are probably trying to exploit the system by spamming their ad in false hopes of getting more exposure.

  • Should users be blocked from creating duplicates?

  • Alternatively, should the user be allowed to create duplicates, but severely penalize the ranking of all their ads?

  • If either of the above system is implemented and a scenario arises where two people claim the same address, how should a legitimate owner of an address prove that their ad should be considered the "real" ad?

  • Isn't it possible that one household will be selling more than one item and consequently need more than one advert in that household? Commented Jan 21, 2017 at 7:47
  • @DarrylGodden that would imply more than one house exists at an address
    – davidtgq
    Commented Jan 21, 2017 at 13:59
  • Really? Sounds like you information architecture needs some work. Commented Jan 21, 2017 at 19:05
  • What happens with condos? Same street address. Are condos "houses" for the purpose of your site?
    – MMacD
    Commented Jan 22, 2017 at 19:49
  • In Poland every condo has its own address, so depends for what country it is.
    – Ada
    Commented Jun 21, 2019 at 14:24

2 Answers 2


What I would recommend for you to do is create a administration system, for each ad that someone tries to create it should request a photo of a bill from that address may it be a electricity bill, a internet bill.. etc. you should have a team that verifies these with either a yes or no. If a address is entered more then twice, you should send a message telling the person that requested it that a thread already exists for this address and if this is incorrect they can contact you for further inspection. From here you can do another address check on each of the customers.

I don't believe you should penalise people for this because initially that's going to be their first though. Let them try it's human nature, as long as your system has a sort of preventive system it'll work perfectly fine. You'll find that the method I suggested is how larger companies e.g. banks verify addresses.


To penalise would be to discourage the users to a great extent. Arbitrary restrictions are never good. The root of the problem is duplicate ads which can be handled in multiple ways. For example, displaying existing ads in that location when the user is adding the address of the property. You can just rethink the flow to reduce duplicates.

Consider an owner who is not very used to computer and websites, but decides to give it a try anyway. To penalise such a user will be completely unfair and discouraging.

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