As a generalisation - even for information-specific searches, I simply don't believe it, as I'm sure many searchers don't even consider the suffix when they read the serps.
But if it was 'searches about Britain' or something equally specific (just the kind of thing YouGov would ask!), I guess it's fair enough.
Interestingly, I can find many domain-sellers quoting this survey - but not one-single non-domain seller or news site, even using uk-only search. No, I didn't look at every single result, but I looked at a fair few ;)
Slightly more worrying, I can find no reference to it on the YouGov site, and I couldn't find one domain-seller quoting this favourable result that included a link to the results source.
All information gratefully received ... my eyes ain't what they were ...
[edited by: Quadrille at 8:15 am (utc) on July 7, 2007]