There's usually very little difference.
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June 2, 2002 - Joni Cesta - Dedicated Caregiver - Profile - NYTimes.com
http://www.nytimes.com/2011/01/09/opinion/09rich.htmlIt was in his eyes all along, she had said, and she trusted in him despite signs to the contrary. "Not too many people would do that," he said.
What is the difference between "trust in someone" and "trust someone"?Even in post-shellacking mid-December, polls found that Americans still trusted him more than Washington’s Republican leaders to fix the nation’s ills — health care included, according to the ABC News-Washington Post survey on that question.
So "trust someone" is informal?