custardo it would be relatively easy to put a status line across the top of a thread saying "This thread is linked to on " (where gives the name of the site, and if possible, a web link to a specific post/ page).
When you hover the mouse on a link (on MN, for example) the browser shows the destination (as an example, assume a BBC web page).
When you click the link, Mumsnet takes you off to a website called 'redirectingat.com' and includes the web link to the BBC page. (I think redirectingat.com is only used by big websites and when there's a link to some company site that pays commission, they replace the link to make it pay MN for the click)
When the browser has gone to the redirectingat.com site, that will forward on to the BBC link. If it had gone direct from MN to BBC, the BBC web logs would show a request for some specific BBC page, and also can record the web link pointing there.
In the case of someone on FaceBook putting a link to a MN thread, the MN server would be able to have a record of the referrer page (on FaceBook) and the MN page. So if those were stored, the MN page could show a link back to the FaceBook page and 'warn' people that there was a direct link.
It would need some effort, however, either to check the web logs every day (which would mean there'd be a delay before MN could show the warning and link), or some code added to each page (a big overhead).
As with most technical things, there are possibly ways I've not come across to do it, which may be much more efficient.
I don't think it was a comparable situation - no wish to ask Twitter to take it down, though if some other site was slagging off MN, and pointing web links at MN, then it would be a relatively easy way to find the other site, but it's rare anyone would have the time.
There's a service called SiteMeter which reports on visitors to websites, and that can show me what browser was used, what ISP user is on, and even what they typed into a search engine to search for. But with thousands of hits a month, I tend not to look at the stats very much. Most web hosting has stats showing a proportion of the info, but grouped together so one can see stats like
Visitors by Country:
Great Britain (UK) 69.3%
United States 9.3%
India 6.8%
Australia 2.1%
Ireland 1.8%
Pakistan 1.4%
(details above were for MumsNet)