I think that there is a fundamental miscommunication about what is unique content. You've asked how a ticket broker could offer unique content. They can. But to understand how, you need to focus on "unique" being "one of a kind" - something no one else offers.
Consider a ticket to hutcheson's Southern North Dakota Symphony for tonight (6/23/06), Section 1, Row B, Seat 3.
Someone buys the ticket, and then enters it into the database. Immediately, hundreds (thousands?) of websites can offer that ticket. It is not unique to any one site. Someone who wants that ticket can go to many, many places to get it. Why is it helpful to the user for us to list thousands of sites that are all offering only this Section 1, Row B, Seat 3 ticket?
The answer is that it's not particularly helpful at all. I know I don't want to click on 20, or 200, or 2,000 sites only to find the same ticket for sale on all of them. What a colossal waste of my time.
Now, consider another ticket broker, who buys the seat at Section 1, Row B, Seat 4. This broker keeps the ticket in his hot little hands, and doesn't enter it into any shared database. It's only available from his business and his website.
That's unique. If I want to sit in Section 1, Row B, Seat 4 tonight, I have to go to him, and no one else. If he has a bunch of tickets that he - and only he - can offer, then we have a very good reason to list his site.
The problem is not that a company offers a database (lots of listable companies use the same back-end software), but that the database contents are shared, and that all the members are offering exactly the same products. This isn't even a case of very similar, almost identical, products, such as 2 copies of the same book, or 2 different tickets to the same performance. It's not a case where one company might be out of inventory, but another might have it. Every client of the database company can offer me Section 1, Row B, Seat 3. But none of them can offer the neighboring Seat 4. And when Seat 3 is sold, none of them can offer me anything at all. But the lone guy with Seat 4 could.
From our perspective, the database clients are all offering exactly the same product. If the database clients had one listing in our directory, and the other broker had one listing, a surfer could find the two available tickets in just 2 clicks, instead of hundreds or thousands. Our hope is that he could find all the available tickets (note: not necessarily ticket sellers), and still actually have time to get to the symphony...
We have decided that it is not in the directory's best interest, or the best interests of our users, to list hundreds or thousands of companies offering exactly the same product. That's not going to change anytime soon.
The database company stands to benefit (from increased sales through their database) by making a list of the businesses that use their site; we do not, and our users (the websurfers) do not. If the database company - or an association of their clients (that's you, by the way, hint, hint) - wishes to make a directory of agencies to help increase sales, that's fine with us. You (or any other company) can do whatever you wish with your own sites to market yourselves.
It is not our purpose to market anyone's business. We exist to help surfers find unique content. If some businesses benefit from our listings, that's entirely a side effect of our users benefitting from the unique content they provide, and our listing of the site. It's nice for everyone concerned, but it's not our raison d'être.
You may have an excellent site (I have no idea). If you do, and if you focus on useful marketing/promotional strategies, you will probably get lots of business. If the only content you have is from a shared database, I'd think twice about making Dmoz an important part of your marketing strategy, since it will not likely be listed. But I'd say the same to almost any business. There are plenty of other, more productive, ways to promote yourself. I'd focus on those.