If they see houses being flipped in their neighborhood it's easier to be mad at the flipper than at some anonymous banks or agencies far away.

What I (and some of my wholesaler friends) have done is got a mailbox from the post office (USPS), and used that for return address.This provides some anonymity and privacy while you'll still get the returned/undeliverable letters - and this is good because:1.

I read that it's better to invest using a trust than a LLC because it provides anonymity, more protection and doesn't require filing with a state.

From reading other posts, I've gathered that:1) LLCs can over asset protection2) LLCs can offer anonymity However, in this particular case, there is another entity in between me and the properties owned (the syndication's entity). 

Just note that there is a limit to the anonymity.

It would give you a layer of anonymity and add outside liability protection.For putting assets in the LLC you just do an assignment that will be your contributions to the LLC.

@Steve FitzgeraldTrusts provide anonymity and the LLC a corporate veil that can isolate assets from other assets so one catastrophe can't take down the empire. 

Or is it too late to hide anonymity 

I was wondering if it's possible to remain anonymous by forming an LLC in CA.

Write anonymous letters letting them know they are being watched.