I went through the same thing once. I also had a woman on craigslist who continually copied the wording of my ads for her own. I take a great deal of time and thought to the wording of my ads and it frustrated me that she copied them exactly so it appeared like it was the same ad and i potentially lost out on responses. I sent her numerous emails nicely telling her how much i appreciated the compliment but she could take the time to write her own ads as it wasnt doing either of us any good. she didnt stop, so i changed my ad regularly and she finally gave up LOL. I did have someone who constantly took my mailbox signs down and its frustrating for sure. she must have alot of time on her hands to be doing it. just perservere and repost signs. as for the ones that cost you money, i'd probably sit and watch to see who comes to take it down. You can check out Vistaprint, you can order magnetic signs for your car and they are really inexpensive. good luck and hopefully the karma gods are watching.