What is a key guideline established by the Federal Trade Commission regarding marketing information?

The key guideline established by the Federal Trade Commission (FTC) concerning marketing information focuses on managing the "Do Not Call Registry." This registry allows consumers to opt out of receiving unsolicited telemarketing calls, protecting their privacy and reducing unwanted disturbances. By enforcing rules about telemarketing practices, the FTC aims to ensure that companies respect consumers' preferences not to be contacted, fostering a more ethical approach to marketing.

The other options do not align with the FTC's primary guidelines. For example, unsolicited emails are often regulated under different sets of laws such as the CAN-SPAM Act, rather than being encouraged. Similarly, promoting direct mail advertising does not have the same level of oversight by the FTC as telemarketing practices do. As for requiring all companies to share customer data, that would raise significant privacy and security concerns, which the FTC would seek to mitigate through various data protection and privacy regulations rather than establishing a blanket requirement. Thus, managing the "Do Not Call Registry" stands out as a fundamental part of the FTC's commitment to consumer protection in marketing.