A few years ago I worked with uprival to create an ad network for our clients - it was pretty easy process from them as they had previous experience in this area but also very helpful when needed at times! They were really responsive throughout out entire project (and even after!). Their customer service is top notch too. Honestly there isn't much that i dislike about how things went down or anything else like that so if you are looking into buying ads then definitely check these guys!! We used UPRIVILEDGE which allowed us give advertisers more flexibility over where & what types of advertisements could be displayed across various websites/blogs etc..