Getting the chain of footage you need - even with enthusiastic cooperation - takes days if not weeks to complete. Most folks are not great at providing this, and most consumer security cameras kinda suck. You're dealing with cops and residents who are not the most technically proficient, so a bunch of random different video files provided via e-mail, USB stick, etc. takes a lot of time.

I have direct experience with this and Chicago PD asking for my and my neighbors footage for a carjacking that happened in my alley. It took days for everyone to respond, and by that time it's pretty useless until they catch the crew responsible and just add that charge to whatever crime they actually got caught doing in real time. This can take months to years to happen. CPD is not great though, so you always need to take things with a giant grain of salt. However, the problem is legitimately difficult even if everyone is acting in good faith.

I'm not saying this in support of Flock at all. I do not support their use since it's so trivial to abuse the capability. But the capability is there and very useful if used correctly - that's why it's such a concern. Not worth the security vs. freedom tradeoff for me. Especially when you look towards the future of how an even more robust network and better technology will be used in practice.