As per the subject line.

I'm entering the world of Android through Netrunner, so I don't really know the setting much. Is the number of factions for story/setting/thematic reasons?

Or is there a specific mechanical reason for it besides the particular strengths and weaknesses each one has?

Or- most likely- it's combination of both?

Why not have just 3 Corp factions instead of 4 to match the 3 Runner factions? Doesn't the extra Corp faction spread cards out a bit more so that Corp decks resort to using Influence more than the Runner?

I'm just curious. Thank you for your time.

While I can't say for sure, my gut intuition is that it comes down to what they felt they could fit, and the diversity supplied by those options. Going higher than 7 factions obviously dilutes the fact in specific card options even further OR removes the capability to just combine neutrals and one faction for an easy one-box build-less experience.

At the same time,it's clear that more identities are better for promoting diversity in feel and play style. This goes for factions, as well.

So given that 7 ends up as the magic number, why do Runners get the fewer number? Becausw , unlike Corps, all of their cards except the identity itself can be taken cross-faction. Agendas can't.

Going with my gut this is my reasoning for the faction split:

The Runners are based on the ICE breakers: Shapers are particularly good with Code Gates, Anarchs with Barriers, Criminals with Sentries. This split also creates the factions themselves. Code Gates in tend to be cheap for their effects but don't tag or damage the runner (Tollbooth, Enigma) so Shapers end up being the "Consistent Cash Flow" faction. Barriers end the run and act like barriers, so Anarchs are built to break the barriers down; they're the "Trash" faction. Sentries are built around nasty effects, traces, and tags, so Criminals are anti-tagging and burst Cash Flow to pay off the Traces.

The Corps are based on the 4 major effects you can put on the runner: Net Damage for Jinteki, Meat Damage for Weyland, Brain Damage for Haas Bioroid, Tagging for NBN. Splitting the factions like this colors what different factions could do for balance reasons. Brain Damage is easily the best type of damage, so Haas Bioroid's ICE has a built-in back door; HB also is the only faction that can't reliably win by flat-lining the runner. Net Damage is usually about slowing the runner down rather than winning, which is why Jinteki ended up with Nisei MK II. Tagging is about slowing the runner down in a different way: while Jinteki forces the runner to spend clicks drawing cards, NBN makes the runner spend clicks taking credits; NBN ends up being the Speed faction with cards like SanSan City Grid that the Runner can't really afford to Trash if the Corp is doing his job right. Meat Damage is about flatlining, so Weyland is built around the only card in the game that can consistently flat-line: Scorched Earth; to balance Weyland, the Corp must go out of faction to get good tagging tech or must sacrifice agenda points for his best ICE or effects.

That's my 2 cents for why the factions are split this way.

Thanks for writing all that! As someone just getting into the game and looking at deckbuilding it really helps me have a base understanding of the different identities.

Another reason could be that it fits a design formula established by Call of Cthulhu that has 3 Investigator and 4 Monster factions.

I have a feeling it's because in the future it will be easier to change the runners for variety than the corps.
Just give a new Shaper identity card and it's not a thematic problem. There's no limit to the number of identities for the runners. It's also real easy to mix and match cards from different decks in a runner deck.

Can there be two Jinteki corps cards? There are not two corps dealing with psychic bioroids in the Android universe… Also, half their cards are tough to move from one faction to the next… The corps decks need to be much more "focused" than the runner decks to work.

As such, you need more variety from the go for the corps over the runners, which are more flexible.

deedob said:

Except we already know there will be multiple identity cards for the corps. The first data pack has the new Haas Bioroid identity in it.

While I agree with most of the analysis of Sydwys8, I don't think the runner factions are going to be particularly good with one type of icebreaker. And you didn't mention what seems to be the exclusive domain of Anarchs, the viruses. With the paracites and data-suckers the Anarchs are going to want to focus on cheap low strength breakers. Meanwhile it seems like Shaper programs will come with "for the rest of the run" standard. I predict that in future sets we will see an Anarch Decoder with similar values to the Corroder and an Shaper fracter that functions similar to the Gordian Blade.

Anarchs are destroyers. They trash deep into R&D, and they destroy ice.

Criminals are money machines. They generate piles of cash, and either run straight through and buy off the consequences or bribe their way in the back door.

Shapers are the faction that likes to attack the biggest challenge they can find. They build their rigs to prepare themselves for anything, and their run-duration pumps let them run down long chains of ice incredibly efficiently. They pick the biggest, most well defended fortresses, and just walk through the walls, at a cost. Once they get set up, if the Corp hasn't won yet, the Shaper has their number.

That's the best way to characterize them. Yes, each of them has some icebreakers that are considered to be quite efficient, but that's a byproduct of presenting a poorly balanced set overall if one faction has all the best tools. It's not meant to be a defining characteristic.