I guess the "list URLs" side of things might be an awkward abstraction, although it'd let you merge multiple services which could be cool too. I use IFTTT to move starred pocket items to Evernote, so that'd be one possible use case if Evernote also implemented it.
Pocket was added to Firefox because Mozilla wants the extra revenue from partnering with Pocket.
Also, anyone implementing a compatible backend can switch to it by changing a pref.
I see a comment below from a Mozilla employee stating that "there is limited public information available about this deal", and claiming that the best quote is in an article that contains a paraphrase from an email from another Mozilla employee saying that Pocket didn't pay for placement.
When a non-profit gives prominent placement to a for-profit company, there are many ways for money to change hands beyond straight up payment for placement. I think we are owed a clear explanation of the Mozilla-Pocket deal.
I've been pleading internally for an official public response. Nothing.
The only other source I've seen is an email reply from Mark Mayo at http://www.planet-libre.org/?post_id=18514
I was enjoying the Firefox reading-list feature because it allowed me to save webpages and sync across my devices without having to put all that information into a proprietary 3rd party service. I thought the reading-list was one of the best features added to Firefox for years, and now they have scraped it. I really can't understand how Mozzilla executives came to the conclusion that this was a good idea.
To paraphrase: it seems they wanted a reading list feature but found it pointless to re-implement an existing solution with many desired features. (Work which was started but appears to have been scrapped.) This rationalized piggy-backing on Pocket. It gives Firefox a reading list for its users without Mozilla having to maintain it.
My personal problem with this has more to do with the anti-competitive nature of integrating services rather than Pocket's closed source.
[1] https://groups.google.com/forum/#!topic/firefox-dev/B3jJq_kU...