An example of a trademark that is highly descriptive is the recently filed mark above. The applicant filed this application in Class 032 for "[l]emonade" on March 13, 2016.
A mark is merely descriptive if "it describes an ingredient, quality, characteristic, function, feature, purpose, or use of the specified goods or services." TMEP 1209.01(b). Additionally, slogans are not registrable with the USPTO if the slogan is "merely informational in nature, or...common laudatory phrases or statements that would ordinarily be used in business or in the particular trade or industry." TMEP 1209.03(s).
The reason these types of marks are not registrable as federal trademarks is because the law believes everybody should have the opportunity to use descriptive words and phrases to describe their goods or services (rather than give one entity a monopoly over the term).
Is the phrase FRESH SMASHED LEMONADE descriptive of an ingredient, quality, characteristic, or feature of lemonade? Is it informal or a common laudatory phrase ordinarily used by lemonade sellers? Probably, especially if the applicant is offering lemonade that is made by smashing fresh lemons.
When this application is assigned to an examining attorney at the USPTO in approximately three months, I have a feeling an office action refusing to register this mark for being merely descriptive of the goods offered with it will be issued.