"Effective July 1, 2008, all travel on United, United Express, Ted, Star Alliance and partner airline* flights credited to the Mileage Plus Program will accrue actual miles, with no minimum. This change affects only those flights that are less than 500 miles."
Here is the link
Before, all airlines credit the actual mileage flew or 500, whichever is greater. US airways changed the policy last year to actual mileage flew. now UA joins, I am sure within few months, all other ailrines will join together.
Another devaluation of mileage programs.