The emerging interest in realistic controlled experiments in computer science has created a need to examine related research ethics. Increased realism and scale in experimental studies pose new challenges that have not been debated to a sufficient extent. Specifically, there can be conflicts between the ethical principles of scientific value and informed consent. This paper provides an account of related previous work in computer science research ethics. To illustrate, two large-scale software engineering experiments with industrial participants are described. Challenges and solutions in these experiments are discussed in the light of current ethical guidelines. Interviews and debriefing sessions with industrial participants from these, and other, experiments are also provided. These reveal that there will not necessarily be ethical problems with increased realism, provided that the researchers respect the principles of informed consent, benefice and confidentiality.