For me, wireframing and prototyping are two separate stages of the design (i.e. pre-coding) process - agree with Rahul; they're not the same thing.
We try to keep any initial conversations to wireframes - simply ensuring we have the core information architecture of a page/application right. Keeping wireframes lo-fidelity makes shifting, resizing, adding and removing elements, etc. all quick and simple.
Once we reach agreement with clients on those aspects, we can begin to add logic and functionality to give a representation of the interaction - this is where the prototypes and increased fidelity comes in.
This would be our approach in an ideal world. It is, as you know, very rare for projects to sit in an ideal world. Sometimes, you'll meet clients who'll be very experience driven and simply won't get lo-fi wireframes - they'll need colour, imagery, functionality and sample content to really get their heads round what you're going to deliver. Alternatively, you'll get clients who will totally get the wireframes and will have a set of requirements which are fine-grained and detailed enough for you to construct without additional time/effort of prototyping.
You need to have the skills to do both, but what you spend your time on and how much detail you go into will be governed by your type of client and commercials.