Oh, they're crowd-sourced internet UGC - of course they're subject to manipulation. But frequently having something is better than nothing.

I think it's ultimately a positive thing to have a mechanism for users to flag content as being questionable and have that flagging be subject to some kind of court of public opinion.

If anyone spends much time on Wikipedia they're familiar with this kind of public debate. Community Notes are a bit like a less sophisticated Talk page. Obviously it's imperfect and obviously ideological shades leak through, but it's still better than forum-style god-mod autocracy.