Two contradictory thoughts.
If companies wish to disseminate commercial information using a syndication protocol then they need a news aggregator that can supply authentication credentials to the server. Some already can, but, depending on their compatibility with the authentication methods available on the server, it is possible they will be transmitting usernames and passwords unencrypted over the internet. This is clearly a Bad Thing. If Digest Authentication were reliably available then this would mitigate the problem. This would be an appropriate solution for a company wishing to set up a public, but paid-for, service.
For the type of information my company wants to disseminate, we would prefer to issue our customers with a digital certificate. I am not enough of a security guru to comment on the relative merits of this technology compared to username/password, but I know it is the norm in my industry (financial services) to operate like this.
Here (at last) is my point: the first news aggregator to offer digital certificate authentication is in a unique position. Not only is it likely to be widely adopted in the financial services industry, to the complete exclusion of its competitors, but it will also generate a good deal of publicity among some very influential consumers, for syndication technologies in general. Blogging will have grown up all of a sudden.
What is the downside? Well although financial services is a large and influential industry, it isn’t mass market. If, as a news aggregator product owner, your business model is to make $0.02 from everybody on the planet then it’s probably not worth building this. On the other hand you would like to sell to an industry that doesn’t mind paying top dollar for the right technology then go right ahead and add this feature.