Yes: it is their own business and they should be able to do it if they want.
Yes: but only if their employer agrees and they are open about it with their affiliates.
Yes: but only if they are open about it and do it to understand affiliates better rather than making money.
Maybe: I think it is a very touchy matter even if it is out in the open.
No: I think it is just plain inappropriate for an affiliate manager be an affiliate too.
No: Affiliate mangers should be prohibited by their affiliate programs from being an affiliate under any circumstances.