Any reasonable person knows to be weary of any ranking, after all there is usually some subjective criteria by which the position in the ranking in judged. For example, how does one determine wealth ? Is it cash in the bank, assets, potential assets etc.
The same care should be taken with MBA rankings, which often have a very strong weighting towards salary increase. You should be aware that this might be the reason many MBA schools are keen to recruit young students (their potential earnings can only go up !). Also watch out for fluctuations in exchange which may cause disproportionate salary increases when adjusted to the US dollar (or British Pound). Another often considered factor is the International flavor of the course, but many of us have dual nationalities and this figure can easily be fudged. Faculty members qualifications and academic contribution is also often weighted, again there are various ways in which this figure can be fudged.
All in all, you should not choose and MBA by it's ranking unless you are concerned with the fact that a prospective employer may be interested in the ranking of the university you attended (which would be very unfortunate indeed).