There's a discussion going on in the UK about where miles earnt on business flights are really owned by the business and should be used for offsetting future business flights. See link. I'm guessing that things like VS Flying Co will head this off as it provides a clear distinction between miles owned by the employer (Flying Co) and those by the employee (FC).
This is one of those rumbling stories that have knocked about for a few years. Personally I think there's quite a good deal of hypocrisy going on in regard to MPs who are only doing what thousands (millions?) of others do. But there's added hypocrisy if government employees are forbidden from doing it yet MPs are not.
On a personal level, I see the use of miles as a reward / perk for the amount of weekends I spend travelling unpaid to meetings in different continents on Mondays or Fridays, for the 15hr+ days I work etc.
As to company policies, there's always the tax man hanging over these things, if a policy expressly makes it OK then I guarantee some Inland Revenue vulture will work out the taxable benefit!