This comes as no surprise as Google recommended you target “All available sites” in their Network:

For those who know the AdWords system, “All available sites” include Google’s Content Network. The content network is a great way to gain brand exposure across Google’s community of websites, but certainly not recommended if you have a limited budget and want to run a very targeted campaign.

Instead of choosing “All available sites” – select “Let me choose…” and then tick the boxes “Google Search” and “Search Partners”. Leave the content network box unticked.

The above settings will ensure your adverts only appear on the Google.co.uk domain and their  partner websites.

Google must make a lot of money from new advertisers unwittingly burning money very quickly on the content network. If Google were a little more transparent when making their recommendations it would no doubt be better for the new advertiser and more likely they would continue using AdWords instead of writing it off as unsuccessful.

Coming Soon:  Choosing the best Keywords and Match Types.

Enjoy