Good news - the premium CPM for enhanced creative has been abolished in DoubleClick Campaign Manager. Technically, the file size in DoubleClick Campaign Manager is now unlimited.
For more detailed information about display creative features for DoubleClick Campaign Manager, please refer to Google's support article.
Although we're excited that the extra fees have been removed, if your campaigns are executed programmatically through DoubleClick Bid Manager (whether you are using DoubleClick Campaign Manager or not) there are still restrictions to consider. The limits imposed by exchanges need to be adhered to.
Refer to the DoubleClick Bid Manager Help article for creative details and specifications for the largest exchanges. However, it is always wise to refer to the IAB guidelines if you are ever in any doubt.
For a long time, the IAB has recommended a 40KB limit for standard display creative. This is intended to ease the load on the various technologies needed to deliver an ad and more importantly, mitigate bad user experience on publisher sites caused by the latency of ad tech delivering creative. There are always exceptions when working with publishers directly, but within the network (and now through the programmatic space), standardization has continued to remain important.
There have always been methods to circumvent this restriction - polite loading is the recommended form of ad delivery as 40KB can be restrictive to creative freedom. However, when programmatic was in its infancy, rich media and video were a distant vision, and the industry was concentrating on refining the delivery of standard banners through the new complex series of ad technology needed to complete an RTB auction. While doing this, the file size limit was restricted to 40KB as the exchanges needed to protect their publisher partners from a new form of latency caused by an increase in systems involved in delivering an ad. If this embryonic technology was going to be able to mature, the support of publishers was (and still is) essential. I'm sure, in the early days, reduced hosting and bandwidth costs were certainly a welcome effect for the young companies pioneering in this space!
This was reflected in DoubleClick Campaign Manager by the pricing of delivering ad creative - if your creative files were 40KB or less, they qualified to be on the lower tier of CPM cost. Any creative that exceeded that (but wasn't rich media or video) would be classed as an 'enhanced creative' and a premium would be levied to the CPM. In the world of RTB and Programmatic, things could be worse: ad exchanges previously would not let your ad serve through their systems at all and then potentially blacklist your other campaigns.
Final thought - Protect the Ecosystem
Latency and disruptions in user experience on-site is a key driver of ad blocker take-up and can contribute to bad user sentiment directed at the industry, and even particular brands, if users perceive their ads being responsible for interrupting their browsing. It's in everyone's interest to create good quality, well-targeted creative that is coded well - think of it as providing excellent customer service.