From the FAQ, it appears Guardian Witness is quite keen on the syndication idea, but not so keen on saying outright that the witnesses would be paid, how much or exactly when. They might be paid "according to circumstances",
Our Terms & Conditions also state that, by submitting content to us, you authorise the Guardian to allow third parties to use the content, and this may include re-distributing items of content on an individual or wholesale (i.e. as a content feed) basis. In the event that a trusted third party - such as a broadcaster or another newspaper - contacted us to express an interest in appropriately using GuardianWitness content - for example a particularly powerful image or video - we would endeavour, but would not be bound, to contact contributors, and this may include, according to circumstances, entering into a revenue sharing agreement. link
We may use content incidentally in our own house advertising campaigns, for example to market GNM products and services. link
They would also like to sell ads against Witness contributions,
In the normal course of our business, advertising will appear across the GuardianWitness site. link
Secondly, about this thing called the Internet.
In 2006 the Guardian's own former digital guru Emily Bell slammed the National Union of Journalists for a proposed code of conduct for a scarily familiar sounding "Witness Contributors" code of conduct.
If the Canutes who wish the internet had never happened looked around, they would see dozens of services offering words and pictures on all manner of topics without a single professional or paid-for contribution, none of them traditional media organisations. link
In the eight years since that was written, there are slightly more than dozens of services allowing anyone to upload anything. And I suspect I'm still more likely to upload stuff to 1) a place where my friends are already and 2) to a place I believe won't try and make money out of me/advertise against me/use me for internal marketing campaigns.
Lastly, there's one other thing that grates slightly. It's about core journalism skills.
Over the last ten years I've trained hundreds of journalists in how to find stuff out using the Internet. One universal from that experience is that a 'they come to you' system is just not good enough. It's like swimming in a goldfish bowl when there's a bloody great lake on the other side of the window. There's more useful stuff in the lake.
I don't for one minute expect Guardian journalists to disregard that big lake, which makes me wonder how useful Guardian Witness will really be on both big and niche stories. It's often the honest, no axe to grind voices which yield the most authentic content and in 2013 finding those voices online is an essential journalism skill. Requesting submissions from a "community" might yield some of those voices, but it looks lazy and possibly ineffective and definitely more of a minefield of vested interests and large axes to grind.