Don't keep a full VersionHistory. Instead, use a system like KeptPages or EditCopy that regularly forgets past versions. Don't implement FilteredRecentChanges such as a WritersLog that allow you to easily dig past the RecentChanges. Don't keep an AuditTrail. Don't keep a ChangeLog?.
At extremes, automatically delete any page that's not been edited for a month, unless it's been marked as a CommunityWiki:StablePage (see the SpaghettiWiki proposal)
If your community allows you to HardBan or KillFile, or to use a CommunityWarning, then automatically time out these features. See DynamicValue.
You can emit <META NAME="ROBOTS" CONTENT="NOARCHIVE"> to try to discourage archiving by google and other external sites. For robots that don't respect the noarchive tag, you can use a SurgeProtector. If you have a big site, a defective internal search engine, and block external search engines with no-archive, this discourages searching for half-remembered content. You can rely on this to enforce a kind of SecurityByObscurity forgetfulness - ensuring that old content will only be blundered upon accidentally.
You can't do this perfectly - there's no way to prevent someone from manually archiving particular versions of particular pages - but you can force them to make a conscious decision to do it. Equally, although a lack of archives can hinder full accurate remembrance, there's no way you can stop the partial and distorted remembrance performed by the brain. Indeed, by obscuring memory in software, you encourage memory in people, which actively hinders ForgiveAndForgetInWetware. Similarly, if you wear a watch, you don't store the time in your head.
The above text is PrimarilyPublicDomain
ViewThrottling (as implemented in ProWiki) is another way to discourage external archiving. When the access rate surpasses a limit (e. g. 20/Min) the IP is blocked. If it falls again below a different limit (e.g. 5/Min) it is unblocked. -- HelmutLeitner
I changed the text to what I think you meant.
This is not a great page title: Software can't forgive. Really, this is something like ForgetInSoftware? (except that sounds worse).
Software can forgive through DynamicValues. A SurgeProtector forgives by allowing access again. A negative TrustMetric can forgive by forgetting ratings. Forgiveness means to accept the other person, to give bearing to them, to pardon. If you'd like, forgive applies to actions/behaviour, and forget applies to data/reputation.