As far as I know "ambition" in English and Russian means not always the same. In Russian it may have a negative implication. For example:
"Он очень амбициозный человек" may mean that the person is given a negative characteristic.
On the other hand, this word doesn't imply anything negative in English as a result it may cause a misinterpretation. But it's rather a subtle thing, I must admit.
Read about it here: Ответы@Mail.Ru: что означает слово амбиции