Requiring student to participate in online challenges to complete coursework I'm teaching a programming course with ~20 students, guiding them through coding assignments and helping them understand what they are doing, and why it works or doesn't. Tasks expected of them range from trivial to medium-complexity in the range of a 40-hours curriculum.

Now, toward the end of the course, they know enough to solve moderate programming problems. In order to get them to work on a few things more "exciting" than what we offer them, I am considering asking them to join an online coding (or problem-solving-through-coding) competition, such as Project Euler. I wouldn't expect them to be able to solve all problems, of course, but I could select a list of problems for them to pick from. For example:


  For this session, you are expected to solve between 5 and 10 problems from the following selection of Project Euler numbers: 1-10, 13, 15, 20-24, 26-29, 33, 35-38.


Sure, I could just copy these problems and make them "assignments" for them, but I think it could bring some fun for them to see it as part of a competition. Also, why I don't understand why, it seems that to their generation, doing anything online is vastly more exciting than doing the same thing otherwise. Finally, I have some hope that a few students might actually get into it, and continue doing it for fun after the course.

Now, comes the question: what downsides do you see to requiring them to participate in one of these online challenges? (I'm most interested in the specific case I detail above, but generic advice/answers for other types of online participation might be interesting too!)
This sounds like a great idea to me overall, but I can see a few potential issues:


It's possible that one or more of your students might already be a participant, which could raise issues of fairness.  (Other students may complain that he/she got a head start.)
Similarly, the fact that these problems are widely distributed on the web may make it easier to find solutions online.  I haven't looked at the Project Euler solutions online and don't know if they are any good, but it's not hard to find purported solutions.  This could also be a pain for you: if you make it easy to cheat, then you're more likely to have to figure out how to deal with cheaters.