Cost - NDAs are perhaps the lowest cost of protection for an invention. Often a simple agreement can be obtained for little to no cost. Although cost is one of the primary benefits of NDAs, this advantage has a tendency to breed over reliance. Breadth - NDAs provide broader protection than patents, which is a reason justifying simultaneous use of NDAs and patent applications. Breadth includes both positive and negative aspects.
Broad protection is beneficial at nearly any time.
Most NDAs, however, struggle in determining exactly what is and is not covered under the terms of the contract. A common example is where there is no recording of what information was communicated during the discussion. The ambiguity can lead to problems should the matter ever come to litigation. The disclosing party wants the contract interpreted broadly including all information related to the actual disclosure, whereas the disclosee may wish to interpret the coverage much more narrowly. This can be a costly issue to resolve.