Can't say about pg, but I left Twitter (I'm a regular, non-blue user) because the ads lately got out of control. Every other post is a promoted ad from a totally unrelated category, which I can't relate to. Ads targeting either stopped working, or Twitter allowed large numbers of low quality advertisers to push their ads.
I turned my ad-blocker off a while ago, out of curiosity, and my ads have been a mix of (mostly) no ads at all or (occasionally) a bunch of ads at once for really strange things. One time I got six ads in a row for locations in China. Not tourist spots, mind, but stuff like a dig site in a Chinese city. Another time I got amateurish Christian evangelism and a guy promoting a article in Nature about cats recognizing their names. I'm not even sure why the second guy was promoting that article, as they were neither a co-author nor affiliated. Very rarely do I get ads that are even remotely related to the kind of accounts I follow on Twitter.
I experienced a similar phenomenon. I have 2 accounts, the latter following very few people. So it’s showing almost exclusively ads and promoted tweets since there is nothing else to show.
