"Death by PowerPoint" refers to the over-use of PowerPoint as a presentation medium both in business and in educational contexts. Do a search in Google and you will find numerous occurrences of this phrase.
When PowerPoint first began to be used as a presentation medium it looked impressive: the "wow!" factor. But after you've seen 100 presentations it gets as boring as any other medium. What you have to bear in mind when using any presentation medium is that you still have to work hard to get your message across, particularly in the foreign languages classroom, where you have to combine presentation with lots of practice with your students.
See the TES article (1 September 2006), Death by... PowerPoint, by Michael Shaw, who writes:
"The problem - dubbed 'Death by PowerPoint' - arises where the popular Microsoft program is used to teach dull, didactic lessons. Where once trainees were told to avoid "chalk and talk", the new hazard is 'click and talk'."
He continues, citing Roger Higton, Lord Williams School, Thame:
"The teacher may feel very pleased and think they are up-to-date and modern – but the student will glaze over within the first 30 seconds. Students find this passive absorption of knowledge no more educationally creative than copying out of a textbook."
The message is: Don't rely just on the presentation. Presenting new vocab or points of grammar with PowerPoint does not guarantee that they will be retained by your students. They need to practise using the new vocab and grammar.
Have a look at this amusing video on how NOT to use PowerPoint:
Life after death by PowerPoint
by Don McMillan
See also ICT4LT, Section 4, Module 1.4, headed Whole-class teaching and interactive whiteboards.