Placebo of clinical trials are ethically acceptable provided that patients receiving placebo are not at risk for serious harm and give informed consent

I have heard of a situation where participants of a pharmaceutical cancer trial got together in a room following a group informed consent session and combined their meds and then divided them out so that all the members of this group would have an equal fraction of the active ingredient. This is possible for rare diseases where members are part of a support network. Perhaps this says something about a flawed information session process (although the research scientist was a very reputable scientist in the RCT arena), but it is also an interesting comment on peoples need to do something that might give them an advantage with their disease.
I guess the question is whether there are any alternative options to a placebo controlled trial that might still provide useful information. Does one need to wonder that if the difference from the current best treatment is so small for a new drug that it cannot be ascertained that it is really worth pursuing, unless there are other benefits such as reduced side effects? I am not an expert in randomized clinical trial (RCT), but that would be my question. Would not selection bias also be a problem if those responding to conventional therapy are less likely to risk missing out on this to go on a placebo controlled trial versus patients who are not responding to normal therapy, who are more willing to try for any chance of improvement.