There is a rumor floating around the philatelic world that the American Topical Association is going to be changing it's name to include the word "thematic." In the U.K. and other places in the world topical collecting is known as thematic collecting.
There is already an Indian Thematic Society, a thriving organization, as well as an affiliated chapter to the ATA located in Ludhiana, India.
Topical or thematic (you say po-tay-to, I say po-tah-to) gains more active collectors as the specter of the impossibility of putting together a complete country collection grows with every year's flood of new issues.
From my own experience (Lighter-Than-Air philately, with a specialization in balloon posts) I can attest to the endless fascination involved in putting together a good topical collection. Without the pressure of having to buy a country's most expensive items -- including rarities -- topical collecting can be pure enjoyment.
Meanwhile, if any reader can verify or quash the rumor, please feel free to do so in the comments below.

Comments
This rumor is totally not true. The ATA has no absolutely no intention of changing its name. As a matter of fact, in my “Jack’s Journal” column in the May-June issue of Topical Time, I noted very good reasons NOT to change the name, including legal ramifications and tradition. I wrote “By far the most important reasons not to change are philatelic. Collectors often enter the hobby be choosing a topic. That’s what many call it – a ‘topic,’ not a ‘theme.’ The American Topical Association needs to be there for beginning collectors. The philatelic entry door needs to be as wide as possible.
“Many topical collectors don’t want to expand their topical collections to become thematic. Since every thematic collection also is a topical collection, but not every topical collection is a thematic, the word topical is more inclusive… The ATA, is, therefore, all encompassing – it is for new collectors, for those who are content to be topicalists and for those who decide to become thematicists.”
I neglected to note on my previous message that I am writing as the president of the ATA.
Thanks very much for the facts, Mr. Denys. Continued success with the ATA.
John Finch, About.com Stamps