Disadvantages (occasionally abbreviated as DAs) are types of arguments that have also found their way into Lincoln Douglas after a long tenure in policy debate. Disadvantages are often characterized by long link chains and large final impact stories like extinction or nuclear war. While the format may seem intimidating, in reality disadvantages are no different from normal arguments, and accordingly, you should treat them as such.
When to Use Disadvantages
Disadvantages, while very similar to normal arguments, benefit from their slightly different form. While much of the time, the focus of a constructive is on providing a solid framework through which you can interpret and filter impacts. In contrast, disadvantages are independent pieces of offense that because of their large final impact, tend to operate under any type of a standard. As a result, their is much less focus on debating the standard, and a lot more emphasis on debating over actual arguments.
Another benefit of this style is that it's possible to read multiple disadvantages that seemingly have no relation. Disadvantages are in general employed by negative debaters, as a very modular strategy that makes adapting easy. Because disadvantages often do not depend on each other or on a common framework, it is very easy to switch individual disadvantages in and out.
A disadvantage has a slightly different set up than the normal claim-warrant-impact structure you're probably used to. While all of these elements are still present, their presentation is noticeably different. Namely, the three sections of a disadvantage are the uniqueness, the link, and the impact.
Uniqueness
The uniqueness section is probably the section that is most foreign to you, and in here you describe the state of the world as it currently is. This description should pertain to the type of argument you want to make. For example, if you want to talk about how the implementation of the death penalty would lead to huge amounts of problems in the judicial system, you should describe what kinds of problems (if any) the judicial system is facing now.
Uniqueness is important because it directly correlates with how strong your impact actually is. Taking the previous example, if the judicial system was already overburdened, adding more problems while bad wouldn't be as devastating as if the court system was running well for the first time and was about to be ruined. Thus the uniqueness controls how strong your impact is.
Further because uniqueness is a description of the status quo, the more recent your uniqueness evidence is the stronger it stands up to criticism. Additionally, this serves as a great way for you to defensively engage a disadvantage. If you can disprove their claim, you ultimately weaken their impact. This argument is called 'uniqueness overwhelms the link'.
Link
The link is much more intuitive, and you can think of it as a long extended warrant. In general, the link section is where you demonstrate why taking the action of the resolution would be bad.
Because of the nature of a DA and their large impacts, often time multiple links are needed. Each of these smaller links in the larger chain should be independently labeled, but it is perfectly acceptable to have a long chain. Further, doing such can be advantageous. Each link in your chain has its own warrant and its own impact, and it is that impact that is used to propagate the chain. Thus, each mini-link does have an impact and can be used as offense in that way.
The danger with having multiple links, however, is that all of the links are needed in order to prove the final argument true. Thus, even though you are able to come up with many smaller impacts with this strategy, you run the risk of having to spread yourself thin defending each individual part. In order to counter-balance this problem, if possible you should try and come up with multiple link chains for your story.
Impact
The impact is the final section and ultimately the most intuitive of all of them. The impact is exactly the same as it is in the claim-warrant-impact structure, namely the reason why your argument is important. Again, because of the structure, the impact should be as big and broad as possible, so it denies the possibility of it being excluded by a particular criterion.