I have read in LDCE for Advanced Learners (2009) that 'when you mean that you care about smth a lot, say that it is important to you, not that it is important for you' and for instance in Face2Face Elementary (2nd edition) they teach you to use to be important to smb but I have come across on more than one occasion the exact same phrase with preposition for in coursebooks. I wonder what it means and whether there are any shades of meaning in usage in these two prepositions in the expression above.
In this context for refers to a purpose and to refers to a personal valuation.
It is important for the crypto-photographer to remain absolutely quiet if he hopes to capture the Yeti's courtship ritual.
It is important for you to bring enough supplies on this mission.
These skis are the right size for you.
Making lots of money was important to her.
To her it all seemed awfully vague.
For the crypto-photographer to capture the Yeti's courtship ritual, he must remain absolutely quiet.
For you, these skis are the right size.
Do you see how you as the "intended user" qualify as the skis' purpose?