SPOX has been built upon the same engine as ideone.com and spoj.pl, but dedicated to teaching in the context of private lessons or regular courses at different levels, starting from beginners to advanced university students.
Yes, collaborative debugging might be the case to use ideone. You might for example want to provide the input data to someones code to show up bugs in it.
IDEdroid seems to be cool, thank you for the link.
But I can not agree with marginality. First, the situation when people are asking for help is quite common. Second, there are more cases when such services might be useful: experimenting with a new language, comparing/demonstrating the behaviour of a particular compiler, sharing groups of pastes (lecture examples?), and more.