Warren - 11:44 am on Jul 10, 2004 (gmt 0)

Sensis have that database because of their Yellowpages product.

Not only that, they know which business have web pages because:
1) They are listed on YellowPages online
2) They are in their printed Yellow Pages ad
3) From City Search
4) From a crawler (potentially).

So now they have the database to mine and the hungry sales people out there to turn it into sales.