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If you take a look at the number of work units output by Sourcefinder here: https://gridcoinstats.eu/project/sourcefinder,
you'll see that they have been very few and far between. This means that tens of thousands of GRC have been minted for almost no work. Each user achieved some magnitude based on a small number of work units, and since there was no more work to be done, everyone's magnitude remained about the same, despite the fact that no work units were being crunched.

Several other users have mentioned this on Steemit in the past, but as far as I can see, there is no concerted effort to stop this. The most recent example of this is actually in the thread right below this one, by @applepiie: https://steemit.com/gridcoin/@applepiie/an-update-on-the-threadripper-experiment.

One by @parejan (in this one, he specifically mentions delisting): https://steemit.com/gridcoin/@parejan/wu-availability-for-gridcoin-whitelisted-projects-17-jan-18

And another one by @parejan, pointing this problem out practically from the beginning:
https://steemit.com/gridcoin/@parejan/gridcoin-whitelisted-project-sourcefinder-out-of-work

Although it is mentioned more than just those times.