But it's just not done! And some would even say it's bad grammar! One must always try hard not to purposely displease authoritative grammarians.
But seriously, regarding split infinitives like the one above, one must think of grammatical clarity. Compare:
The police decided playfully to raid the truck.
The police decided to playfully raid the truck.
Was it the act of deciding that the police did playfully, or was it the act of raiding?
According to one online guide:
The argument against split infinitives (based on rather shaky historical grounds) is that the infinitive is a single unit and, therefore, should not be divided. Because it raises so many readers' hackles and is so easy to spot, good writers, at least in academic prose, avoid the split infinitive. Instead of writing "She expected her grandparents to not stay," then, we could write "She expected her grandparents not to stay." Sometimes, though, avoiding the split infinitive simply isn't worth the bother. There is nothing wrong, really, with a sentence such as the following:
He thinks he'll be able to more than double his salary this year.
According to The Oxford American Desk Dictionary, the rule against the split infinitive "can generally be ignored", "is not firmly grounded" and "can lead to awkward, stilted sentences."
Today's dictionaries allow us to split the infinitive, but it should never be done at the expense of grace.
To boldly go where...