Kay16 -
In many fields, it is common to have large teams, and in multiple sites. In health research, for example, it contributes to the generalizability of findings (e.g., does treatment A work as well in location A as it would in location B where conditions are different?).
Ethical researchers utilize their respective professional/academic organizations' guidelines regarding publication ethics. Here are some examples:
Ethical Guidelines to Publication of Chemical Research:
http://www.chem.ucsb.edu/~laverman/Ethics/pdf/ACS_ethics.pdf American Association of Health Behavior: Publication Ethics:
http://www.ajhb.org/2005/6/NovDec1205Laflin.pdf Medical Journals Publication Ethics:
http://www.wame.org/resources/ethics-resources/publication-ethics-policies-for-medical-journals/ Note that these guidelines indicate that being the senior PI for the research project that generated the data is not by itself adequate reason to be listed as co-author!
I have taught an academic writing course for our doctoral students. In the past, a very few faculty exploited that class as an opportunity to get their names of publications. My philosophy is that I am being paid to teach the class, and reviewing and helping the students thru the process is part of the resoibsibilities of teaching this course.
So, the first thing I cover IS research and publication ethics. I have students put in writing the agreements they come to with each other, their advisors, co-authors, whoever about authorship responsibilities, timelines, authorship order, etc.
I work to ensure that my help toward developing the paper ends when the term ends. If substantial more work is required, then they should seek their co-authors/advisors. If I am asked to continue working on the paper, it needs to meet my requirements (e.g., in my area, etc.) and the agreement is modified to include me with the full agreement of other co-authors.
Frankly, I've co-authored only 1 paper this way - it took a full year past the end of the term to get it published (with us working weekly on it). For other papers, I am acknowledged - and that is fair.
Finally, I also try to convey to grad students that (a) they tend to over simplify the process of writing publications, (b) tend to over-estimate their own writing abilities, (c) tend to overestimate their own contributions, and (d) don't realize how much work their faculty advisors actually have to perform to make papers publishable. This is due mostly to time! Faculty typically do the same amount of work more quickly - due simply to having more practice and writing and editing. All the grad student sees is that it took Prof A a week to turn their part around, but took grad student 2 weeks. So the (incorrect) assumption is that grad student did more work. No. Prof did it more efficiently.
Anyhow, the practice you seem to think is common (adding on names, piggy-backing) is not as common as you might think. Most of us work hard at what we do, take credit for our work only, and do so while helping others advance as well.