Recently PPB has been more public about their use of undercovers/informants to target individuals for arrests.
Some brief thoughts on what that means:
1. This isn't a new tactic, and PPB publicizes it intentionally. Half of the goal of undercovers is to cause fear and suspicion.

2. Informants don't make arrests, riot cops do. If the crowd (or individuals targeted) can safely get away before riot cops engage, PPB is unable to act on whatever intel they get.
3. Consider other actions, not inaction. Smaller non-public actions avoid the risk of undercovers.

4. Fashion choices. Many folks, while in all black, still have 1 or 2 things that can distinguish them from those next to them in the bloc. Change shit up.
5. Act as a crew. Banners and umbrellas can protect someone while they take action and disguise who is responsible for what.