For one reason and another, not all Smart Tag recognisers are available
on all the programs that support smart tag recognition. For example,
according to the Smart Tag technical documentation (SDK documentation)
smart tags that rely on the grammar checker cannot be used in PowerPoint.
Unfortunately, the documentation is quite scrappy and incomplete, so it
is difficult to be certain
a. which tags rely on the grammar checker (for example)
b. exactly where each type of tag's settings are specified
c. whether enabling one option sometimes silently enables other
options (as sometimes happens with Office XP Smart Tags).
However, the Microsoft Office site does state that the Person
Name(English) is available in Word on English-language installations,
and also that it is not available in PowerPoint.
Peter Jamieson