Favicon display seems rife for abuse. I wonder what happens if you put a favicon that looks like googles’ or that says “ad”. All sorts of fun to encourage clicks onto a malicious site because it looks safe.

I guarantee you will have people putting favicon looking like a check-mark or an arrow to make people click more.

Correct. There could be quite a bit of fun. This more than likely could work for sites not in the top spot. If you borrow the credibility of another brand you could get a boost. This click thru boost could then translate into higher rankings over time as you outperform your spot.

I have already seen seen some ascii stars in the URLs of Googles ads. There is always abuse.

I would hope they've put thought into that and might even blacklist sites that try to steal other more popular sites favicons. I guess it would catch a lot of false positives with companies making new sites on new tlds that might share favicons.

According to the twitter announcement, they are not "backtracking", they are going to experiment further.

As of today, search results are still favicons on mobile...