Just seen your questions .... I buy a lot of things online
using paypal and visa (anything over �50 with visa only)
from UK USA Singapore, HK, china etc etc for quite large sums of money <�2000.00... and sometimes requiring customs certificates etc
I've had a couple of problems recently because I'm in the process of moving house ... so addresses are confusing some of the verification services (dabs.com are real sticklers) and use the barclay verisign on all transactions (better safe!).
in the last 5 years I have never ever ever been asked for anything other than recent transaction details (by barclay's - and only when I rang them in response to a card query).
I won't even let my credit card out of my sight when paying in a restraunt these days .... certainly would never send an example of my signature (unless it was my "theatrical" one which is nothing like the one I use in normal life).