george, i hear you on that. i've been working with an e-mail2thoughtxml gateway w/PB pro (a hassle since the xml needs to be imported every so and so) to achieve what you are thinking of. The idea of adding an rss-reader into PB would definitely enhance PB. That way a simple rss-push would add it into PB, typed thoughts and all, attachements included..., yay! Way to go.
I would support this on uservoice, because what we need is a quick way to enter thoughts while on the road. Make this mobile, simple but mobile. Or interface it with reQall or anything.
One of the things i struggle most with when using PB is its interoperability with other software. I don't use Outlook or the like so a simple thing like getting mails into PB is kinda difficult. And even though i like the drag-files-into-it approach plus directory importing features w/i PB i especially miss the other way around: PB being open to the world of other applications (exporting XML each time is NOT an option).
Maybe the rss-feed should go both ways and instead of exporting a brain's xml to disk, then generating rss from it with xslt or the like according to handwritten rules, a thought or thought-type could be declared as "RSS-exportable" and automatically generate the corresponding rss-xml to disk (or push it online somewhere). That way one could create RSS-feeds from inside PB and update feeders on mobile phones/ friends computers/ PDAs/ ... and also take along those Todo's etc.
It could even be a selling argument for the Pro-version and an intermediary to a PDA-Version of PB. Actually, i think i don't want to take all of my brain along, just the stuff i need and querying PB for more on the road when the need arises. Such a quick import could be done by searching for a thought name and subscribing to its RSS-feed..
Anyway, sorry for having hijacked this and kind of turned the functionality around, but that's what i came up with. I like your idea!