Well, in general, splitting up only works in a game if the DM can handle it and is prepared for it.
But, specifically for your question ...
in the games I have been part of, splitting up results in the same probability of "bad things happening" as does staying together -- why? Because those who are in the separate groups basically still look at each encounter and try to figure out if they can take the encounter or not; they just have a lower threadshold that they can handle when separated than when together (and the PCs are usually good at recognizing it).
So to answer your question - my opinion would be that of indifference... one option is no more worse than the other with respect to bad things happening.
If a group is more brash and quick to react than ours is, they may find themselves in over their head more often though. So depends on the group in part to see how "bad" it becomes. (and as said above, depends on the DM if it can even work from a meta game standpoint).
YMMV.