Are duplicate URLs in a topic abuse?

Are duplicate URLs in a topic abuse? If so DMOZ is absolutely littered with them. Why can't the database and/or program include this as a basic check?

I could give hundreds of examples (these were found examining the first 5000 categories out of 350000), but here, for those who don't believe me, I give half-a-dozen. Sometimes I am sure it is an attempt at spamming (succesful it seems). Sometimes it may just be over-busy editors, with over-large categories, probably bambouzled by spam attempts (succesful it seems). I leave it as an exercise for the reader to try and guess why each of these instances happened.

Before you all rush to fix these half a dozen, I would say, STOP! Campaign rather for it to be fixed at a programming level - if it's done at that level it should disappear for ever. I observed this phenomenom precisely because the database which I tried defining (for the site www.localpin.com) said that for any given category, the URL must be unique.

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In http://ch.dmoz.org/Arts/Radio/Personalities/

Basham, Doug
Collection of photographs with links to radio stations and personal web sites of radio personalities.
http://www.dougbasham.com/base.html

Basham, Doug
KDWN Las Vegas, Nevada talk show host. Photo gallery, streaming audio, guest information, and links.
http://www.dougbasham.com/base.html

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In http://ch.dmoz.org/Shopping/Consumer_Electronics/P/

Pikabu Electronics
Scanners, CB radios, radar detectors, cordless and specialty phones.
http://www.pikabumall.homestead.com/ pikabuelectronics.html

PikabuMall Electronics
Radar detectors, CB radios, scanners and FRS radios.
http://pikabumall.homestead.com/ PikabuElectronics.html

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In http://ch.dmoz.org/Arts/Music/Musicology/Ethnomusicology/Organizations/

International Council for Traditional Music
The world organization that supports the study and practice of all musical Traditions, including Urban and Popular musics and dance, all music research and Ethnomusicology. The ICTM organizes World Conferences, Colloquia and Study Group meetings in all p
http://www.ethnomusic.ucla.edu/ictm/

International Council for Traditional Music (ICTM)
A world organization (UNESCO NGO) that supports the study and practice of all musical traditions. Includes bulletins, meeting notes, and links to ICTM-related meetings.
http://www.ethnomusic.ucla.edu/ICTM/

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In http://ch.dmoz.org/World/Euskara/Aisialdia/Ostalaritza/

Ostalaritza eta sukaldaritza Bizkaian
Diputazioaren orria, bilaketak egiteko prest.
http://www.bizkaia.net/Bizkaia/euskara/ Informazio_orokorra/Ostalaritza_eta_sukaldaritza/ eu_resta.idc

Ostatua eta matorduak Bizkaian
Bilatzaile batekin, herriz herri non jan eta non lo aukeratzeko.
http://www.bizkaia.net/bizkaia/Euskara/ Informazio_orokorra/Ostalaritza_eta_sukaldaritza/ eu_resta.idc

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In http://ch.dmoz.org/Society/Work/Workplace_Discrimination/Age_Discrimination/

Overqualified professionals network
A place for older porofessionals to meet, support one another and chat.
http://www.adusa.com/opn.htm

Overqualified Professionals Video Chat Network
Network of overqualified discriminated professionals, network with peers for help, support and jobs.
http://www.adusa.com/OPN.htm

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In http://ch.dmoz.org/Society/Issues/Poverty/Welfare/

Mathematica Research: Research on Welfare and Work
Research and analysis of welfare and work-related programs by Mathematica Research, a respected for-profit research organization.
http://www.mathematica-mpr.com/WELFARE.HTM

Mathematica Policy Research
Research and analysis of welfare and work-related programs by Mathematica Policy Research, a for-profit research organization.
http://www.mathematica-mpr.com/welfare.htm

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In http://ch.dmoz.org/Computers/Consultants/Databases/

Network Centric Consultants - Oracle database consultants for installation, migration, upgrade, diagnostics, application development, and data warehousing. Offers information on technical support and training courses.
http://www.ncsltd.com/

Network Centric Consultants - Oracle database consultants for installation, migration, upgrade, diagnostics, application development, and data warehousing. Offers information on technical support and training courses.
http://www.ncsltd.com/
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It's not abuse. My experience would suggeat that a non-working URL was changed to a working one, but it could be a software bug which kept an added site from overwriting an identical existing one. Also, maybe, something was moved from one category to another one where the URL was already listed.

It's not abuse per se (in other words most likely it wasn't intentional), but it is something that will corrected. Thanks.

I'll put my hands up and say that it's happened to me too.. the URL change thing is the most common way of having the problem. You can't actually add two entries with the same URL to a category, it is essentially a bug/feature.

Side note - the workaround for editors is always to move a site back to the unreviewed queue when changing the URL, and then re-publish it.