I have tried bum marketing in various niche markets like gizmos, electronics, apparels, ebooks, softwares, medical products, and many others as well.
But bum marketing has worked best for me on the medical products. Specially those medical products, about which, people don’t prefer to discuss with their family/friends. For these type of products, they do their research online. Bum marketing at ezinearticles.com or other similar places are good places to present the product reviews for people to tell them which product actually works and which does not. If you are actually helping them in decision making, you will also make the money.