This is what Fowler says in his classic Dictionary of Modern Usage (1926).
The English-speaking world may be divided into (1) those who neither know nor care what a split infinitive is; (2) those who do not know, but care very much; (3) those who know and condemn; (4) those who know and approve; and (5) those who know and distinguish. Those who neither know nor care are the vast majority, and are happy folk, to be envied.A Dictionary of Modern English Usage: The Classic First Edition
Grammar For Dummies
Pocket Fowler's Modern English Usage (Oxford Paperback Reference)
The Language Wars: A History of Proper English. by Henry Hitchings