Feed aggregators (inoreader, feedly) make this difficult, though. One request may end up serving any number of end users, so you can't personalize ads the same

Feed aggregators (inoreader, feedly) make this difficult, though. One request may end up serving any number of end users, so you can't personalize ads the same way. Good, you might say, and I wouldn't disagree, but Google et al sure would.