Real estate is a huge market, so it's no wonder that it's a hotbed of activity and innovation for data publishers. It all started with the Realtor.com site operated by what is now Move Inc. in a venture with the National Association of Realtors.

With nearly 1 million listings updated virtually in real-time, a good user interface, non-gratuitous use of maps and video, useful calculators and other tools, multiple revenue streams, there was a wealth of useful information there, well organized and easily accessible. We gave it our Model of Excellence award in 2004.

Two years later, Zillow burst on the scene. It was a sure-fire combination of clever data aggregation coupled with the guilty pleasure of being able to get a sense of the value of your home (or your neighbors or friends) with just a few clicks. Zillow became an overnight phenomenon, and with an aggressive schedule of new features being rolled out, seemed to be barring the doors to competition. We gave Zillow a Model of Excellence award in 2006.

I was surprised then that, with these two tours de force, Trulia.com burst on the scene quickly thereafter, taking elements from both Realtor.com and Zillow and combining both sale listings and property valuation data in one place. The user interface tries to help users visualize listings by representing them as flags on an area map, a refreshing concept in many ways, but one that gets annoying when lots of properties are for sale in one area and the flags start overlapping each other.

Have we seen it all in real estate? Apparently not. Now HotPads.com has launched. Call it a Trulia for home and apartment rentals. It relies even more heavily on maps for its user interface, and has out-done Trulia with even more extensive neighborhood reference information.

Does HotPads.com now represent the state of the art in real estate data offerings? Ironically not, and therein lies a lesson. The clear trend in real estate (as in other markets) is to load in more content, add more features, give away more for free, and outdo the competition with Web 2.0 cleverness. HotPads wants you to navigate visually through a map that is so dynamic and flexible it is beyond frustrating. HotPads displays buckets of data on every city, obscuring the listings that are its ostensible reason for being. Indeed, only after you realize that the little building icons on the maps represent rental information can you even get close to apartment listings, and even then, you never actually get a list. Apparently you are expected to click on building icons one at a time for detail data. In short, it's a mess that didn't need to be a mess.

The lesson: Successful data publishing means quick, easy access to accurate and relevant information. Deep data is good, but larding up your database with marginally useful content (and then presenting it first) doesn't help the mission. Nor do snappy Web 2.0 interfaces that offer more confusion than clarity. In short, HotPads could do a lot more for its users by doing a lot less. Cool is not a business model.