Well, the challenge is now over, but it was quite a success: I gave out over 8k in plat to intrepid mappers, and the wiki now has a total of 31 zones mapped (with more hopefully on the way thanks to the efforts of Mauxe, who has continued mapping long after he stopped being rewarded for doing so).
Thanks to everyone who participated, and to everyone else: if you ever use this feature to find an NPC, you have the people in this thread to thank for it
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My bank account will need some time to recover, but when it does I'll be sure to hold another contest, so keep your eyes open for it, and again thanks to all who helped the wiki!