We have all seen corporate recruitment spiels on the EVE-O forums about corporations being "small gang PVP". Whatever that is, it depends on the eye of the beholder, but the general consensus at which everyone is comfortable calling a gang small is around 6-8.
of course, reducto absurdum advocates have found the gap between small gang and solo PVP (in a non-lowsec "solo" PVP meta where you need a GTFO Falcon and a link alt for true solo PVP) and they have filled it with the concept of the "micro gang".
What a micro gang is, to me, is a way of advertising the fact that you would do small gang PVP but lack the numbers. This is therefore a concept created by people who lack the ability to organically organise a corporation into anything much at all, or are having a hard time recruiting, or their 80-man corp is composed entirely of AFK toons who've un-subbed but they haven't booted them because it looks bad to have a corp of 12 toons and makes recruitment more difficult.
These are essentially zombie corporations where the survivors of an apocalypse of lapsed subscriptions keep the shell of the reputation shambling around. They probably get recruits every now and then based on their reputation, earned long ago with deeds and members long since passed and dead and subbed off. People join them, find out it's not as advertised, and quit again.
Examples of small and micro-gang zombie corporations are;
R3d Fire who is beating the micro-gang drum fairly hard right now (basically it's Tim nering and alt, and itinerants who seem to log on once a week). Average gang size is about 4 - probably the upper limit of "micro-gang".
Adhocracy - 291 toons but only 34 showing up on killboards in any month, and firmly a small gang PVP corp judging by the average involved being around about 8. Lot of corpses there, shuffling around, propped up by 250-odd dead toons and dead accounts.
There are many more.
While I think that the idea of micro gangs is naff and useless in the majority of applications - it's like a small gang where half of you signed off or went AFK - the term does hit its stride in a few cases where, for example, you have a very constricted entry and limited mass to bring through the hole and you still want to take the fight.
One example of a real micro-gang engagement i can recall seeing was Isogen 5 vs Krannon of Sherwood. iso 5 brought a pair of Moros, a Naglfar a Bhaalgorn and a Loki in against Krannon's escalation fleet, wiped the floor and Zoidberged out of there.
That's a micro gang because the choice was for Iso 5 to drop a shitload of T3's and Logi onto the same target, or to roll in with 3 dreads and absolutely minimal support, in a one-way trip through a single hole. It's the ultimate YOLO.
Calling yourself micro-gang when you've got 3 cruisers and are hunting any given low-class system through the usual set of wormholes is taking a bit of a lend. You fly 4 cruisers because tht's all you can field due to numbers. Or small gang wise, you fly 8 because that's all you've got. You don't make a choice to leave behind 20 toons and other players and restrict yourself in any way and not blob the fuck out of your foes - we all would, if we could, let's be honest.
So that's my take on micro-gang meta - a euphemism for zombie corps and small corps without enough members. And on that measure, Sudden Buggery is a small to medium gang corporation.