It might be a good idea to take masters if u are final year student right now. Why? In order to sit out the economical crisis. But it mostly goes for those doing Economics or Finance. However, it might be good idea not to take it right now if u want to start or already have your own business.
If you are in the UK. Try to change/choose your course so that you would have joint Masters degree with BSc this way you will spend only one year doing Masters and you will be applicable for the government student loan which you are not if you do Masters separately. Then try getting a year internship between last bachelors year and first masters. Internship say at IBM will look so much better on your cv then plain masters degree.
Finally, if you have a research field you are interested in go for the masters and then maybe phd. If you invent smth new that might serve a good head start for your own successful business. But if not that into research find a job for now. Seek that your employer would pay for your masters and if he does: well it couldn't be better to be a freshman once again =]
ps. masters do not have to be in your field (you could argue), try to broaden your perspective. Study economics or a language. In Computer Science there are so few girls, not in arts tho,no.....