Adam Curry is taking a stand on RSS, which for him means "against necho".
Adam admits to paying Userland $10,000 to be included in it's default feed-list and states he made a commitment to a format. In Adam's mind, the necho effort threatens that format and therefore threatens his investment.
Adam, if you're reading this: nobody reads your feed because the format happens to be RSS. They read it because they're interested in what you have to say, and because your feed uses a standard format. Feed consumers don't care about the format, as long as it's supported by their favorite aggregator. Right now the standard formats are RSS 0.9x, RSS 1.0 and RSS 2.0. Adding a fourth standard, even if it's not backwards compatible, will not obsolete any of those.
Necho's success or failure will not force you to change your format, and it will not stop anyone from reading your feed. RSS will remain a standard format, supported by all aggregators, whether Necho succeeds or not. It is not a threat to you in any way, shape or form.
So I'm invoking an age olde american tradition of letting my wallet do the talking. I will again invest $10k in aggregator default placements this year, but I will spread it around, to all developers who adhere to RSS2.0. Include (N)echo and you're out of luck.
If you want those default placements, maybe this would not be a bad investment, especially given that Radio is not the #1 aggregator anymore that it was 1.5 years ago. Which aggregators should you invest in? Well the ones that will give you the most new subscribers of course, but herein lies the problem: if necho becomes a success, any aggregator that does not support it will surely lose market-share, thus diminishing your investment.
If I were you, I would want to invest in aggregators that currently have a large market-share, and that are actively updated to keep up with the latest standards, thus ensuring they remain popular. No aggregator-writer will drop RSS support to switch to necho, but adding necho support on top of existing support for RSS may help the aggregator's popularity, which in turn will help you get more visitors.
So what are you so afraid of?