Online Experiments: Ethically Fair or Foul?
http://www.apa.org/monitor/apr00/fairorfoul.html
  peer-reviewed

Azar, Beth
Monitor on Psychology
2000

Abstract:

Online experiments may be helping researchers gather more data faster than ever before, but those advantages are coming with greater ethical challenges--threats to participant confidentiality, questions over whether the participants really understand what they're getting into and the possibility that less scrupulous researchers could steal your ideas.