Google is beta testing a keyword matching option called automatic matching that is scheduled to go live on June 3rd. There has been speculation that automatic matching would be turned on as a default, but according to a comment in a very objective post on the topic from PPC Hero What You Need to Know About Google Automatic Matching, Google advised that Automatic Matching is not going to be enabled when the new feature is launched.
With this AdWords feature, Google automatically uses an advertiser's excess budget to post ads against keywords other than those the advertiser is actually bidding on. Not all advertisers have been invited to test this new feature, but from what I have read not many may want to. According to Google:
Automatic matching shows your ads on relevant search queries not already captured by your keywords. It works by analyzing the content of the landing pages, ads, and keywords in your ad group. It then shows your ads on search queries relevant to this information. The system will continually monitor your performance on these queries and adjust its matches accordingly. Automatic matching aims to show your ads only on queries that yield a high clickthrough rate (CTR) and a cost-per-click (CPC) comparable to or lower than your ad group's current average CPC. This way, your ads receive additional targeted traffic at a similar cost to your current traffic. Automatic matching won't allow your spend to exceed your budget, and it also won't affect the traffic you're currently receiving. In addition, automatic matching will have no impact if your campaigns already capture the majority of relevant traffic.
The challenge of this new feature is covered well in Scott Clark's post about the 9 things he dislikes about automatic matching.
For those running your campaigns inhouse, I would decline this option for now and stay in control of your campaigns and budget. Be diligent about monitoring your CTRs on your keywords, test different landing pages and ads and adjust based on your conversion rates. My first impression of this feature is to not put it into practice until you understand its implications on your campaign.