Enhanced campaigns were announced in April 2013, and became mandatory for ALL advertisers on July 23, 2013. Essentially, the biggest difference between “enhanced campaigns” and “legacy campaigns” is that with an enhanced campaign you cannot segment neatly based on device or operating system. This is a huge change in AdWords, because previously it was considered a best practice to have one campaign setup to target mobile phones, and another campaign setup to target PCs and laptops. Now, they introduced the concept of the “mobile bid adjustment” which allows an advertiser to bid more or less based on whether the target is using a mobile phone or not. At the same time, enhanced campaigns treats tablet traffic the same as PC traffic, which takes a little bit of control away from the advertiser.