The rate of return (ROI) answers are the money gained or lost. It measures a percentage of the interest to the investment, e.g. you gained 5 € on your 10€ investment - the ROI is 5/10=50%. The ROI can be as well negative.
How can we analyse the interest of the investment in online communities? What events cause positive or negative activities in networks? There are some papers trying to explain the matter of things basing on communities contributions:
In Burke et al. the scholars calculated the probabilities of getting a response in discussion boards. The probabilities highly depends on the type of introduction("i'm lurking here for several months" - group introduction or "working as a professional in this area" - topic introduction) and sometimes on the type of group.
The wiki case is observed in "Wikis as social networks: dynamics and evolution", where the vandalism on a wiki page was detected if the page regulates the information flow within Wikis. Particularly, if the page is a hub between many other pages, the probability of trashing is high.
Anyway, it is more complex to find out the ROI for human interactions as to calculate the finance ROI, where monetary values are used. The investements in human interactions and the interests of these are not uniform and hardly comparable. What you know from the childhood: if you use rude words in the conversation, your listener will reply coarsely as well (in most cases). The rule "if ... then ... " is on the stage. If we have the pattern "rude question", will we get the pattern "rude answer"? Why yes and why now? What are dependencies? Shouldn't the activities/events/actions in communities be modeled? Then will modeling be useful to find the provoked profit?
In the informatics there is a bag of artificial intelligence problems like reasoning, learning, decision making. Those are aware or at least try to be aware of all the inconsistencies and uncertanties human interactions have. Those should be used to find the reflective patterns.
