The story they ran does not reliably attribute claims about surveillance to the NSA slides, but adds its own speculative claims and, later in the story, blurs the line between what the document is claiming and what the Guardian believes to be fact.
I don't see where the lines are blurred. If you're referring to what you expressed here[1], I'm not convinced. The story is very clear about the source of the information at the beginning of the article, and it then follows the common convention of not appending the repetitive "according to the source material" to the end of each sentence.
I suppose you could say that some of the statements are speculative in that they say "if the claims in the Prism presentation are true, then...", but I think that's speculative in a very narrow way. It makes sense to draw out possible consequences of the program as expressed in the source material that are rooted in fact and not in speculation.
The article is definitely not speculative in the dangerous sense; it does not say things like "direct access probably means root access to production servers" or "since this program costs only $20 million it's likely to keep growing".
It does make claims we have not yet seen evidence for, but there's no indication they're speculative...
When the FAA was first enacted, defenders of the statute argued that a significant check on abuse would be the NSA's inability to obtain electronic communications without the consent of the telecom and internet companies that control the data. But the Prism program renders that consent unnecessary, as it allows the agency to directly and unilaterally seize the communications off the companies' servers.
