An adgroup houses keywords, a campaign houses adgroups, but which adgroups and keywords are you grouping together and which devices are you targeting where? The structure of an AdWords account can vary as much as the specialists who work on it, and while sometimes not immediately apparent, there is usually a logic behind the structure.
What is important is that the specialist understands the logic – knowledge being power – behind either an inherited or owned account. In fact, logic in strategically grouping keywords and adgroups is essential to running a well-managed account, it is the difference between an easy to manage account and an account that is a chore of confusion to maintain. Getting this right at the outset, again whether inherited or starting from scratch, is pivotal to the work that follows.
Google’s top 3 tips are to  organize your campaigns to mirror your website,  create separate campaigns for different regions, and  use Adwords Editor to manage your campaigns. While all 3 of these are true, they only touch the surface. My intention here in addressing this deceptively simple process, is to look in more detail at keyword match type segregation and what this means for budget allocation and ease of management.
Organizing Keyword Match Types: Campaign or Adgroup Level
There are several schools of thought on this topic, although first we have to ask the question – do we split our keywords out by match type at all? My personal preference is yes, although it is by no means necessary, the main reason being more oversight and control. I would caveat here that it also depends on the size of your account, for a small account it may be perfectly manageable to house a variety of match types within one adgroup.
The second question to ask is, if are going to split up our match types, at which level do we do this? The campaign or adgroup level? Again, the answer to this question depends on the level of control you require in an account.
The benefit of splitting match types at the adgroup level are  that your keyword variants are all in the same campaign, oversight here being easier, and  you can easily cross negative at the adgroup level. By cross negative, I am referring to placing a negative keyword on exact match within the adgroup that houses the BMM equivalent, doing this on your top converting or priority keywords will ensure that your more cost efficient exact match keyword variant picks up on exact searches, while your BMM variant captures any remaining queries/traffic. This method works particularly well if you are fully utilising BMM, rather than phrase, and Exact match keywords, as it ensures that your BMM adgroups or campaigns are not competing with your exact match ones
The main benefit of splitting out match types at the campaign level is control over budget allocation. This is important as you may find that some match types are more cost efficient than others – the general rule here being that Exact is usually more efficient than BMM. By splitting out match types at the campaign level you’re ensuring that you have an added layer of control over where you spend your budget. The shortfall of this approach is that you could lose oversight if you have too many campaigns cluttering up an account, leading perhaps to the perception of disorganization to the specialist unfamiliar with the logic behind the structure of an account.
Don’t Neglect Naming Conventions
Although I have only touched the surface here (for further depth check out What’s A Good PPC Structure Anyway?) there is one final point I need to make and it concerns naming conventions. They are part and parcel of every account, and by that I do not mean adgroup #1, adgroup #2, and adgroup #3. Not only do clear naming conventions allow for ease of management, oversight, and quick insights, they reveal the logic behind your structure. If someone else has to work on your account will they get it? Are you able to locate and manage your keywords and adgroups efficiently? If your answer to these questions is no, you may need to address your naming convention habits.
To conclude, while approaches to structuring an account may vary greatly, it is certain that a structure should be determined by the needs of the account, especially in terms of the level of control required and scope addressed, ensuring ease of management and allowing for useful insights. Here, Logic is always key, and a good specialist takes the time to get it right. In that sense my conclusion is the same as Search Engine Land’s recent contribution in that “the impact of campaign structure is complicated”, but we underestimate it at our own peril, especially because in so doing we can undermine our own ability to manage an account, collect valuable data and even miss insights where the weakness of an account is its foundations.