[Spinball]

tamarian, the situation which leads to the scenario I am taking about here is a link to a specific thread on your site from another site. (or sometimes if you're lucky, more than one site) when something particularly interesting has caught their attention.
Their referer information*should* in the first instance hold the site containing the link to yours.
Perhaps the referer information could only be stored if it's off site.
Although having all the referer information would allow us to show the route people take though the site. Something which may be useful in analysing how well presented and usable your site is.
However, I don't think any of this fucntionality is worth slowing down the forums significantly.
I can't actually analyse our apache logs as they are too big.

[Edit:] My moderators have asked if the thread title rather than the thread number could be shown. I agree that this would be most useful.