Given his ability to communicate with the outside world (it appeared that the station not only had television and presumably internet access as he was often assigned to collect information about people, but also we saw how a person could communicate off island as Ben did with Richard while showing Juliet the status of her sister), Mikhail must be completely trusted by Ben and believed to have absolutely no desire to leave the island, and could not be corrupted into selling what he knows about the island to an interested party such as Widmore.
He also has way more autonomy that the other Others - he is allowed to operate completely on his own without Ben's supervision.
He also appears to be Ben's henchman, willing to do whatever Ben asks, even killing Others
He was lower in the chain of command than Bea Klugh as she demands that he kills her. The person who knows more information would be the one who demands to be shot.
His ability to heal (like Locke) may imply his importance to the island.
Then he should have a higher rank amongst the Others.
The Island heals almost everyone on the Island quicker then normal, Locke, and Rose, were extraordinary cases
Mikhail like several of the Oceanic 815 survivors but unlike the majority of the Others has actually met Jacob. Mikhail says he was recruited and came to the island when he was 24 years old by a magnificent man. He confirmed the man wasn't Ben. It couldn't be Widmore since Widmore and Mikhail are on separate sides. Presumably the man isn't Horace either since the Others hated Dharma, if Horace was so magnificent Mikhail probably wouldn't defect to the Others if he was ever Dharma. Jacob led Mikhail to the island all so Mikhail would be in the right place at the right time and bring about the chain of events that disabled the looking glass station, allowed the freighter folk to come to the island and eventually sent the 815 survivors to 1977.
It could have also have been Richard, when he said magnificent he may have been referring to the fact that Richard does not age. This seems likely as Richard recruited Juliet.
In "Through The Looking Glass", Ben whilst speaking to Mikhail states "You have always been a loyalist"
He may have been conditioned in Room 23 to be cooperative; Bea Klugh seems to have an almost domineering control over Mikhail when giving the order to shoot her and could be evidence of his conditioning.
He doubted before shooting Bea.
He is one of the original "Hostiles" on the Island. While we don't know his exact longevity (i.e. if he is "immortal" like Richard seems to be) he, Richard does not seem concerned about his well-being and none of the Others seem too surprised that he lived through his ordeal with the Pylons. . Given how many brutal beatings he took and still came out unscathed, and the fact that he had no apparent want to get off the Island...
When Locke beats Mikhail in "The Man Behind the Curtain," none of the Others seem terribly concerned about his well being afterward.
Perhaps this is because of Mikhail's healing abilities. We see him survive the sonic fence, being shot with a spear gun in the chest, and lots of abuse. He seems to always reappear.
Mikhail's ability to keep showing up after being "killed" brings to mind the character of "Michael" in the movie "A Boy and His Dog", in which a post-apocalyptic underground society uses a big guy named "Michael" (dressed in goofy farm boy clothes) to enforce their rules; after he is "killed", another one appears, and then another, because "Michael" turns out to be a robot and there is a whole bunch of them.
It also brings to mind the character of Kenny from South Park, who gets regularly killed on the show and brought back, but no one ever says, "They killed Mikhail! Those bastards!"
Mikhail's ability to escape death parallels Charlie's. Perhaps Mikhail was being kept alive (by the island or the universe course correcting) to kill Charlie.
Awareness of observation
Bakunin could have been watching them as well with a hidden camera in that station. He saw them setting up the surveillance and was waiting for them to look at him before turning off his feed.
The camera that Locke saw was the one that redirected back to The Pearl station.
He could have walked up to the camera when the recording light lit up, triggered by Locke who activated it while changing the feed in the Pearl.
This is because the island would not let him die until he fulfilled his duty (killing Charlie) just like the island would not let Michael die. (this is probably in the wrong place)
"My name is also Andrei..."
Mikhail's note that said "My name is also Andrei" is an in-joke, referencing the actor's name, Andrew Divoff.