The drone programme has been in the news again recently

"The campaign of CIA drone strikes against suspected militants in Pakistan has made the United States "the most prolific user of targeted killings" in the world, said a United Nations official, who urged that responsibility for the program be taken from the spy agency.

Philip Alston, a New York University law professor who serves as the U.N.'s special rapporteur on extrajudicial killings, made the comments Wednesday as he released a report on targeted killings. The report criticizes the U.S. for asserting "an ever-expanding entitlement for itself to target individuals across the globe" in its fight against Al Qaeda and other militant groups."

By David S. Cloud, Los Angeles Times
June 3, 2010

Meanwhile, May 30 (Bloomberg) -- "The U.S. military said "inaccurate and unprofessional" reporting by a team operating a predator drone contributed to a February airstrike that resulted in the deaths of as many as 23 Afghan civilians.

The February 21 attack on three vehicles took place because the ground-force commander received inadequate information about who occupied the vehicles and where they were traveling, U.S. Major General Timothy McHale wrote in a four-page report released yesterday. McHale said "poorly functioning" command posts failed to provide the ground commander with evidence and analysis that the vehicles posed no "hostile threat."
U.S. military personnel compounded their error of firing on civilians by failing to report the incident in a "timely" fashion, McHale wrote. The civilian casualties weren't revealed until almost 12 hours after the strike when a surgeon disclosed the deaths at a hospital, the report said."

A widely-quoted study released by the New America Foundation in February estimates that between 830 and 1,210 civilians have been killed by drones since 2004, 30 per cent of estimated total fatalities.

This figure probably refers to inaccurate strikes however rather than those in proximity to a 'target'

As one Pakistani official asked, "Who is a militant? A bodyguard? A driver? A cousin or guest sitting in a hujra next to a militant?"

There is an increasingly elastic definition of 'combatant' being applied by the CIA, which runs the drone programme in Pakistan

Scott Horton, a contributing editor at Harper's magazine and an expert on the law of armed conflict, highlighted the problems: "Under international law, and specifically under the Geneva Conventions, those who render material aid are not so clearly legitimate targets as the US sometimes makes out.

"Bodyguards are clearly legitimate targets, and family members are not.

In the proportionality analysis, however, it can be argued that family members recognise and accept risk of being targeted by remaining in the immediate proximity of their relative who is a command-and-control figure.
Still, I would argue that the US view pushes the outer pockets of currently accepted law."