Good question! Yes, and no.

Yes => in theory it would be possible to buy follows in order to increase your own UA (albeit pretty costly to do so).

but...

No => there are multiple scenarios in which that would prove to be counter-productive. For example:

• depending on the entire follow matrix of Steem, it is possible that by following account X, your own UA decreases, so that give-away could be costly.

• your own UA depends to a large extent of who follows you. It's possible that receiving 50,000 low-UA follows accumulate to the same score as 1 high-UA follow. Losing that one high-UA follow because of "follow-selling" could lower your UA score as a net result

PS: Built into the UA algorithm are damping factors! Those are mathematical tricks to tune the overall UA distribution, when needed.