Let me give a couple of tips to all the advertising companies out there trying to get photographers to place ads in their publications/online. Don't berate the photographer for choosing their own advertising methods.
I just got off the phone with a guy who's caller id came across as YP.com (yellowpages.com). After the normal platitudes about how great the work is, he goes on to question how I advertise, why it looks like to him that I don't want new work/new customers/etc. I tried to explain to him that I am more referral-based and have been cutting my advertising expenses over the last year, but he wouldn't hear it. The tone became increasingly hostile and condescending. That's not the way to look for new advertisers.
Early-on, I did much more advertising. But, as with any business, the key to long-term success is through relationships, and so my goal (and yours too) should be to establish those relationships. This leads to the fun, exciting work we all want to do, because those people you network with become fans of your work. They know you, your style, and what you enjoy! They pick you for you, and not because you came in with the lowest fee.
The world of advertising is constantly changing, whether it's print or online. I know it's very difficult for advertising publications right now to find and keep clients. Start by treating potential advertisers with respect, and you'll go much farther towards establishing relationships with them.