Just an idea that struck me about how Decepticon society is structured (G1 Seasons 1-2, that is - probably wouldn't work for a lot of other continuities but still interesting to think about.)
Unlike Autobot society, which is mostly individualistic and integrated, Decepticons have a hierarchy of subgroups: Seekers, Triple Changers, and various gestalts. "Loners," who have no group of their own (like Shockwave, Reflector, and perhaps Soundwave depending on how you classify his Cassettes) are rare, and generally shunned and disliked, because while subgroups have great loyalty to one another, they feel no obligation to any other Decepticon who isn't "one of them". The only exception to this is of course Megatron himself, who as the supreme leader of the Decepticons is on a different level than these groupless soldiers.
--The reason Megatron left the competent Shockwave back on Cybertron, and made Starscream SIC rather than the even more competent Soundwave? The two of them are loners. Either Megatron subscribes to the general shunning of such Decepticons, or - as is more likely - he sees them as more of a threat. They aren't tied to a group so they're more likely to try and ascend through the ranks.
--Or maybe Megatron likes loners, more than groups. Groups have their ties of loyalty to one another, but the loners can be induced to absolute loyalty to him alone. This is why Shockwave and Soundwave are placed in their positions of authority: Shockwave as guardian of Cybertron, Soundwave as third-in-command (conveniently placed just beneath Starscream, a good place to keep an eye on the treacherous Seeker).
--Starscream is an anomaly, a group member with the ambitious mentality of a loner. He deliberately wants to leave his group behind, and take on a higher position. Thus, his place as a Seeker is only technicality, as the others feel no great loyalty to him as they do to each other - and the feeling of course is mutual. TC and Skywarp would love to get rid of Starscream and replace him with a trinemate who has proper feelings of loyalty to the group.
--Or: Seekers in general are more independent than most groups... Starscream just takes it further than most. Their ties are relatively loose - they have loyalty to their individual trines, but not as strongly as a combiner would feel to the rest of his gestalt. The casual betrayal the Seekers sometimes treat each other with (Starscream blaming Skywarp and Thundercracker for something, or Thundercracker trying to get Starscream in trouble with Megatron) would be unthinkable for a gestalt, but with Seekers it's natural because of their own inherent vanity and individuality.
--Soundwave was initially a loner, and created the Cassettes to rectify this problem. The rest of the Decepticons view this as unnatural and it's one of the reasons they despise him. Meanwhile, they have no more enmity toward the Cassettes than they do to any other group that isn't their own. Also, Soundwave still acts with the mentality of a loner - his leadership toward the Cassettes is more set apart than the leadership of a gestalt or trine leader. In other words, he leads their group but isn't one of them. His position of leader/creator means that the Cassettes accept and fiercely defend him, but the other Decepticons don't necessarily respect that status. Still, they don't dare treat him like they would a true loner because of the fear of retaliation from Megatron or the Cassettes.
--Shockwave, similarly, isn't respected, but he is obeyed. To cross him would be to risk incurring the wrath of Megatron, after all.
--Reflector is pretty much the underdog of the Decepticons because he's in the worst possible situation - a loner without any authority. At least Shockwave and Soundwave are two of Megatron's most trusted lieutenants, and Soundwave has his Cassettes, so no one dares do anything to them. As a result, Reflector generally takes the brunt of the bullying that takes place in the Decepticon ranks, because he can be pushed around without fear of retaliation from another group member or Megatron. His triplicate nature is a sort of defense mechanism, giving the impression that there is actually a group of him, but of course there isn't and any Decepticon who's at all familiar with him is aware of this. It still might have some subconscious deterring effect, though - no Decepticon would generally attack another who is in the company of similar robots, because usually that means a group and a group means the possibility of violent retaliation.
--Technically, Blitzwing and Astrotrain are loners. However, they've banded together because they share the relatively unique characteristic of triple-changing, and because of the disadvantages of being alone. It's not a natural kinship like the gestalts, but neither is it any more unnatural than Seeker trines, which are also usually formed by choice, so they're generally accepted by the other Decepticons. Besides, no one really wants to get in a fight with either of them.
--It could be interesting to show the contrast between Decepticon subgroups and Autobot subgroups like the Aerialbots, Dinobots, etc. Actually, the Dinobots probably are the closest in structure to a Decepticon group, with their loyalty to one another that doesn't always necessarily extend to the other Autobots. The other groups might not understand the extent of the significance of a Decepticon gestalt, though. For example, one of the Aerialbots wondering why the Stunticons don't just get rid of Motormaster. The reason isn't just fear - he's their gestalt leader and holds the group together. If he was gone, they wouldn't be nearly the same cohesive unit and would be much more vulnerable to other Decepticons. The Aerialbots wouldn't be able to understand this, since if anything happened to Silverbolt or if one of them was left alone, the other Autobots wouldn't hesitate to help them.