Giving a vague answer to is another familiar faux pas. For example, "I'm not sure, five years is such a long time away. I could see myself working my way up in marketing, but I'm also interested in finance."
Employers want to know that you know what you want. After all, hiring, training and developing people is an expensive business – if you're going to leave in six months, your employer will have lost both time and money.
While you certainly shouldn't lie about your plans, you can be less than candid if you're considering several career options – only ever speak about your interest in the industry in which the company you're interviewing with operates.
Although specific aspirations will be well received, rigidity in your ambitions won't be, so choose your phrasing carefully. Rather than saying, "I need to have been promoted within a maximum of three years and I'll be really disappointed if I'm not working with high profile clients in five years' time", you could say, "I'd like to have more responsibility in the next three to five years, ideally I'd be working on some of this company's fantastic high profile accounts." The first answer implies that if the company can't fulfil your ambitions, you'll be dissatisfied, while the second answer suggests a little more compliance on your part.