[..] there's the feeling that so much of what I do is basically common sense--something that almost anybody should be able to do, to some extent. Of course, people like me who've been doing it for years and years will [probably] always be a little better at it and know more about it (I like the rule of thumb that it takes ten years to become an expert at anything), but I still feel that with some guidance people who are motivated to learn about it can get pretty far on their own.(from an interview with Steve Krug, author of Don't Make Me Think!", by Management Consulting News)
And they have to. After all, even for companies that can afford to hire a consultant like me, I can't be there every day with everyone on the team as they make the thousands of large and small decisions that affect usability. So even if they hire me, I feel like most of my job is educating people to make the right calls on their own.
That's what I think consulting is about: You listen to clients as they explain their problems, study their context, and educate them about the choices they have to make so they can judge the solutions that will be offered to them on their merits. Oh, and make sure that all the deliverables that you create with them (problem statements, RFPs, requirements documents, sketches of high-level solutions, visionary prototypes etc.) are useful input to those taking the next step.