Along the same lines, digital display planning involves complex interaction with potentially dozens of media vendors. And that's after narrowing the field down from hundreds or thousands that might or might not be appropriate for a campaign. To complicate the matter further, several organizations might be representing the same inventory -- sometimes at different price points. Dealing with each of these vendors is a drawback of what I'll call the static inventory marketplace. Thankfully, we're already moving toward a dynamic inventory marketplace that will make buying much easier.

The rise of ad exchanges, virtual ad networks and non-exclusivity of sales relationships means that we're introducing a certain fluidity to the online ad inventory market. Inventory can float between sellers, and that means that buyers can leverage fewer sales relationships in order to lock down the same inventory. This effect is amplified by ad exchanges, which can let a number of sellers fulfill an order without needing to increase the strain on the buyer, who has time for only a certain number of sales calls or face-to-face meetings each day.

Ultimately, we could have a completely fluid display marketplace where transactions and terms are managed through just one aggregator that clears everything electronically and mediates any disputes. But we're not even close to that yet.

If we did have it, though, it would make it much easier to gauge inventory availability, put scenario plans together and know with a reasonable degree of certainty what the impact of a given display ad spend would be. Once advertisers have that information, digital will be in great shape.

Conclusion
I think we'll see a nice uptick in digital display despite what's going on with the U.S. economy. Even with gaping holes in the four areas I've just discussed, digital is still very accountable. Accountability will attract advertisers despite any need to cut back on marketing. In whatever brave new world emerges in the aftermath of the financial services turmoil, accountability will be more important than ever.

What it boils down to is that digital needs to be able to provide scenario planning much more quickly and accurately, and it needs to shore up its reputation as the most accountable medium by providing success measurement in a language all advertisers can understand, in a way that's fair to the medium.

Quite simply, if we do all this, we win.

Tom Hespos is the president of Underscore Marketing and blogs at Hespos.com.