I could see where it would be hard to manage the personal/professional dynamic within working groups, and how a successful group balances the dynamic in order to create a supportive (yet productive) atmosphere.
Quite right. Leadership is in a very real sense being personal with everyone--in a professional way. In other words, all followers should feel as if they are individually valued and cared for by the leader, but the leader should treat all people with equal fairness. People normally treat their friends better than strangers--and why not? They are your friends. But when a leader does that, it arouses frustration, if not anger, because people feel (accurately) that they are being treated unfairly. Leadership is a professional role with personal overtones.
In other words, people often feel Affiliative attachment to a good leader (they like the leader and feel part of his/her group), but the leader is using Influence strategies to engage a variety of people for a common purpose. As a supervisor in the UK once told me, "Every Friday I go down to the pub with the boys. I'd rather spend the time with my family, but if I don't do this, they won't trust me and won't work for me." The reasoning is Influence, the behavio(u)r Affiliation.
One thing that confuses people about motives is that they expect specific behaviors to line up with a given motives. "Wow, he's selling all the time--he must be really Power motivated." Well, not necessarily. Often salespeople are driven by the Achievement motive--what they want is to score points in the selling game, and one way to do that is to sell, sell, sell. A more subtle influencer won't even be perceived as selling--instead, you freely choose what s/he wants you to do!
Which brings us back to leadership. The Influence/Power-motivated tend to be more alert to what motivates you and as a result will alter their behaviors accordingly. If a person is strongly Affiliative, a leader may say something like "do this for the team--we're all counting on you." If Achievement-oriented, a leader may instead offer "this is an opportunity to do something really new and different--it's a real challenge to pull off." And Power-motivated people may get "everyone's watching on this one--it's a really big deal."
By now most English-speakers are saying "Whoa! This is really manipulative and underhanded, isn't it?" No. It is speaking to people in the language they understand. As long as you are not lying, it's not manipulative, it's persuasive. In fact, people speaking genuinely from their own motive may be perceived as speaking selfishly, or inaccurately. If you have a different primary motive from the leader, you will not hear what s/he intends you to hear--you will filter it through your own assumptions. The trick to effective leadership is understanding what people's filters are, and getting through them.
One way you can spot the motives in others is to listen to the way they try to persuade you or others. Primarily Achievement-motivated people will try to persuade through statements referring to something being better, improved, new, different. Primarily Affiliation-motivated people will persuade by personal or group appeals. In other words, they try to persuade in ways that would be persuasive to them. Primarily Influence-motivated people, however, will persuade by speaking to your motive, not theirs!
I see I've wandered off from the point of behaviors in the service of motives. Even if you are not Influence-motivated, you may have individual behaviors you are trying to use for specific purpose, but the motivation does not align with the behaviors. I mentioned the supervisor being affiliative to influence his staff, and the salesperson trying to influence to get the goal-accomplishment Achievement satisfaction. The question to ask is "what do people enjoy doing?" The Achievement-motivated salesperson enjoys making the sale, not the practice of influence. The Influence-motivated supervisor enjoys influencing the staff, not affiliating down at the pub.
And that's why you can't judge someone by a single behavior--it might not be indicative, let alone the fact that someone can have more than one motive strong! It's the pattern of behaviors that counts, particularly the spontaneous behaviors, which are more likely to come from the gut. That's why I referred somewhere here to reading matter aligning with your motives--but it is the reading you want to do, not the reading you have to do.
Effective leaders are normally very influence-oriented, whether they have the motive or not, which means they are thinking about what do they have to do or say to influence people the right way. Just being influence-motivated isn't enough--you have to be mature enough to think about the long-term impact of your actions rather than impulsive. After all, a punch in the face can be just as power-motivated as coaching or subtle influence--just more impulsive or immature. In short, you have to be professional!