Hi!
I am going to repeat myself a little too.
Of course you can use servlets etc to build services, but the interesting question is (in my opinion) what the consequences will be.
As before, REST is an architectural style which aim is to obtain certain goals as described in the Wikipedia article:
http://en.wikipedia.org/wiki/Representational_State_Transfer
In order to obtain those goals, you have to follow certain principles (also described in the Wikipedia article).
It is possible to follow those principles when developing servlet-based services. I can also develop Object-Oriented software using assembly language - the question is if it is a convenient and time-efficient approach.
Also, my experience is that the more clear
patterns, for instance for developing a service, there are, the more likely it is that the result created by different developers is more similar. One of the risks is that there is no clear pattern how to develop a service using servlets. Using JAX-RS annotations, it becomes, in my opinion, much more clear.
Best wishes!