What happened at UBS last year is ridiculous. And in the light of recent events in the financial industry I understand your concerns regarding employment options after graduation. But those industry dynamics will hit you no matter if you decide to keep working in finance or go and pursue your MBA.
There's also the scenario of people getting laid off all over the place. In that case, you might wish you had gone to business school to come back into the job market when the skies have (hopefully) cleared.
In any case, here's something that might interest you if your primary concern is UBS. Out of my circle who studied in St. Gallen
2 got a job with Goldman (1 in London, 1 in Zurich)
2 got a job with Lehman Brothers in London
1 got a job with Credit Suisse First Boston in Zurich
(and granted, 2 got a job with UBS Investment Bank in Zurich)
I guess you can see where I'm going with this - UBS won't be your only option.