There's no need to use a centralized service. But if you intend to build in a way to *make sure* the content is coming from where it claims then there's little choice other than to make use of such intermediaries. Experience has already shown that spammers WILL abuse weblogs and their comment systems. My point of mentioning use of 3rd parties is to make it clear that the /option/ to use them should be seriously considered when implementing something. It doesn't have to be used, but failure to consider the hows and whys of using them would be a shortsighted mistake. After all, go look at who's done the Perl PGP modules on CPAN...

As for effort without return, think seriously about the complexities of user registration systems. Then think about the security risks. Too many users will use the same password on different systems. One hack and their entire network of sites becomes ripe for being compromised. Not to mention most sites don't even do *basic* login dictionary attack logging and notification. That's one cure that's worse than the disease.

In short, a site can well make use of regular old web input forms. A site could also make use of a back/forth system that helps both the site and the visitor. The site gets helped by having a way to 'be reasonably sure' who's posting and the visitor gets some help in tracking what they post and where. It ends up being a win/win situation here. Yes, it will require sites to implement something new. It will also require visitors interested in this concept to implement something. It's not like it's going to happen without some modicum of effort. Even weblogging required a LOT more effort than just using vi to write your own HTML pages but fortunately easy-to-use frameworks evolved. Likewise an evolution is possible for commenting.