For the most part, and I can speak only about where I live, bandit signs are illegal. And thank goodness for that, since most of them are downright ugly. And setting aside the awful, handwritten signs, does it really help any neighborhood's aesthetics to have signs that talk about "foreclosure help" staked in every corner?
Most of these signs are on private property without the owner's permission, or they are on public property. My take is, if you have to tack your sign up 9-10 feet so people don't take them down, or if you need to get an untraceable phone number so you can avoid a fine, you need to rethink what you're doing.
Sure, it might be effective, but you know that it's wrong (again, in the cases I am referring to). It's like the people who tape a flyer to my mailbox, or stick a business card in a sandwich bag with some pebbles and throw it in my driveway. Now THOSE are two things that drive me batty. (Yes, I am a full-fledged curmudgeon at the ripe old age of 43.)
If a sign is legal and agreeable to the property owner, go for it. I might not like it, but I can't subject the world to my personal taste. (And what a pity that is!)