How much time (in hours) would law enforcement spend to perform this similar analysis technique? Or would this become trivial if a system that performed analysis continuously were built?
I honestly don't know how long it would take them. It would very much depend on their technical sophistication, their experience with writing network analysis code, etc.
I'm not sure it would make the analysis trivial, but you certainly could engineer a system that would have an easy user interface for conducting this sort of analysis on Bitcoin.
For example, the software tools we wrote would probably only require UI work to get them to a first draft of that - we've basically got a fully functional backend system, although I don't think we've any plans of taking it further.
I don't know if you've looked at the SVG we have on the blog, but its a pretty useful way of looking at this data, even as it stands, with hyperlinks to the relevant blockexplorer blocks.
