Seriously bad behavior.

I remove them whenever I see them in my neighborhood. It's tougher when the miscreants climb to post them higher up on trees and poles. Time to bring my ladder.

Name them. Tell everybody: do not use them!

The problem is that this is likely an advertising company who posts signs for a range of businesses. It's possible that the businesses being advertised have no idea of where those signs are being posted and how they are being posted. Perhaps a good place to start is to contact the businesses and ask them if they are aware of the unethical/illegal practices of the advertising company they are paying.

Signs were removed before graffiti department arrived

@Robert: Seems to me that, if you or others take them down so that they are gone before city staff arrive, that reduces the chances of the city taking any action because they don't have first-hand knowledge. I don't know what to suggest about the tradeoff, but it is a tradeoff. I'm going to reopen this in the hope that Public Works will comment.

I agree that personally removing such signs could preclude the City taking action, but that action seems rare. I personally remove only the easy ones, e.g. those installed in tree wells or easily within reach. I have not yet climbed any ladders or trees (including the one here) not do I intend to. In the case of a sign nailed to a City tree, I hope they throw the book at the perpetrator.

Thank you for your report.

Crews will remove tags on City property as quickly as possible, and will forward a “Release Form” to owners of other locations where Public Works can safely and effectively remove graffiti with the owner's permission.

Sign was removed upon arrival