Unfortunately, the recession will affect all revenue streams, not just advertisement revenue. Companies are also going to finder it harder to sell products and licenses.
Seems like this will affect startups at very late stages in their growth. How many of us have even put ads in before the product was effectively done? Not exactly cutting off innovation at the source.
This article inspired me to write a blog post. It's mostly about my own site, but toward the end I mention that an economic downturn's likely effect on Snipshot and Disqus would be that they could find cheap rent easier. If this is wrong somebody let me know.
From both my developer and user perspectives, ads are boring. I hope I never have to inflict them on my users (said the deluded idealist).