I was wondering if this was legal. I thought of a good idea to block competitors from seeing your ads and clicking on them.
Go to your competitors websites and fill out the contact form. Include a link that you are sure they will click on. This page will get the ip in the back ground and save in a txt file or db. The link would need to be on a domain you don't care about and is not connected to you or your company in any way and does not look like spam. You would need to pretend to be a lead. It could be a picture or a link to a fake competitor with lower prices. Make sure it does not look like spam. I would also use a proxy when I do this just in case they know your IP or your IP is registered to your company.
Another route could be to make it look like spam. This would work better if you sent emails to every email address at the company you can think of.