Extracted from In Defense of Contributor License Agreements:
By far, not every project needs a CLA and the small bureaucracy overhead.
My advice is that you use a CLA for any project that meets these conditions:
Otherwise, use your gut feeling.
Extracted from MPL 1.1 Annotated:
We believe wholeheartedly in the benefits of open source development, but not everyone does. Some people or groups may try to take advantage of the work of open source development through claims of patent infringement. This is unfortunate, but it is also reality. We suggest that you be aware of the intellectual property implications of what you are working on to protect yourself and others from falling afoul of someone else's patent.
We should be imposing a CLA
Have a read at the links above
If you have read the previous links, there is really nothing more to say, we hope you understand our point of view and this doesn't stop you from participating.
Contact us if you have any questions or doubts.