Hana is one of the most powerful characters in the show.
Why? Do I even have to tell why? She's able to get into any database she wants, get any information she wants. Now, we add her physical abilities, her knowledge of weapons... I don't think you could get her...
Now, the difference between Micah and Hana is not so big, but at the same time not so small either.
Both seem to be able to "see" the stuff (whatever it's called), as Micah was able to talk with Hana (or Drucker) in the casino site (Heroes evo stuff).
Micah can also "talk" to the machines. We can say, that his power is persuation of machines, giving him infinite power over everthing. He can easily get thru firewalls, virus detectors, password-secure accounts/site/achives (much more easy than Hana). He can destroy information, destroy
material things also, which is the thing that makes me worry.
He could bring down the government, he could destroy OWI (no one else has been able to, but he could easily destroy ever bit of info about it), he could kill nations, for example by destroying important databases (hospitals, pharmacies).
He could make thing explode! Computers, cars, telephones, electric wires (buildings)... Ah, someone tell me his limits...
So, I don't really know why OWI let him go so freely. specially since there are people like Hana, Drucker, Sylar, Peter, Noah, who could get him (and his power) to do harm to a lot of people.
PS. All the examples there are only 1/1000000 about what he could really do