What is a Taxable Gift?

In 1984 the Supreme Court in Dickman v. Commissioner, defined a taxable gift by using an analogy. The Court used the income tax definition of “all income from whatever source derived” to describe how a taxable gift should be defined.
Section 2501(a)(1) of the Internal Revenue Code imposes a tax upon “the transfer of property by gift.” Section 2511(a) provides that such tax shall apply whether “the transfer is in trust or otherwise, whether the gift is direct or indirect, and whether the property is real or personal, tangible or intangible.” In Dickman, the Court decided that an interest free loan was a gift.
Would a family vacation, or providing a party for a wedding be viewed as a taxable gift? This may depend on whether the person paying for the activity is in attendance of the event.