My parents don't even trust Amazon. They use Visa prepaid cards that they fill up at CVS whenever they have to.
Arguably they're doing the right thing and we're all doing the wrong thing. Either way, micropayments are one of those "ideal world" scenarios that are unlikely to transpire anytime soon.
The minor cost may be offset by the fact that getting a post through to a site that has almost no spam because of its filter is valuable in itself. If the bot is sophisticated enough that the stuff it posts is hard to distinguish from a human shill or shitposter it may even prefer sites protected with such a system.
Useful for the vintage VIAGRA HERE link dumpers perhaps though, but those can be filtered out with a content filter.