In the scramble to accommodate for aggregate events manager, and iOS14 updates in Facebook… I’ve seen a lot of people return to the use of interest groups.  Interest groups, were developed by Facebook to compete with Googles affinity audiences. This was done back when Facebook was a PPC platform, before the Facebook pixel existed, before there were Conversion Campaigns, before we had the algorithm, before we had real machine learning, and reliable LALs, and even the EdgeRank system even existed.  So, why are people coming back to interest groups after they’ve been obsolete for years now?  1st off, I have seen a lot of people see success in isolated fashion with interest groups. these can absolutely be helpful at a small budget, where you are unable to leave the Learning Phase, And Facebook is your only source of reliable traffic...  However, historically these audiences breakdown at scale and are far less stable / efficient than broad audiences that prioritize the customer experience and the user flow while matching creative to need.  This will likely not change, and there is no reason that interest groups should perform better today than they have in the last six months or last six years. There is one fundamental reason behind this. The Facebook engineering team has not changed the base code behind how interest groups are populated or implemented in the auction.  In short, Interest groups were obsolete… and absolutely nothing has changed in how they’re built.  What made them obsolete has only been further magnified. Because of this, as it currently stands, and will likely not change in years to come, interest groups ultimately perform a function at an extreme lack of scale, But prove to be a liability when stability, efficiency, and growth are priorities .