Falsifying results in studies or experiments is a serious breach of academic honesty.
A professor at the University of Washington falsified results in NIH-grant-funded AIDS research. He lost his job, had to withdraw his articles from prestigious journals, and received unfavorable news coverage. Also, other people who cited his work had to reexamine all of their results.
People are sometimes tempted to make up results to get more attention or funding, but getting caught (which almost always happens, even if it is years later) has major consequences.