For example - when you have a link relation that is sometimes an array, and sometimes a single link - it can confuse clients to have to figure out when it is and when it isn't. I have built the code to support a 3rd argument to the Resource.link method which is an optional boolean value to indicate forcing an array. If you think it's useful I'll send a pull request.
Here's my work: chadkouse@8e206c3
Thanks