One of the few minor issues would be that IDism would grow massively, mostly from older, veteran players.
Blockland is currently at what, 37-40k ID's right now?
And the game has been out for retail for a number of years now. I don't know the actual rate of players purchasing the game, but it has been as low as 10k a year~ before.
Let's imagine Steam takes on Blockland (or Blockland takes on Steam), and Blockland becomes advertised through Steam. It comes up in searches on steam, adverts, through the steam update news, perhaps daily deals if Badspot were to allow them.
Blockland gains a much larger audience who no longer learn of it purely from either word of mouth, the very rare advert floating around (Are they still even out there?) and from the many people who wanted a Lego game, searched Google and found this.
So, let's say that the Blockland playerbase expands greatly.
Instead of 10k a year growth, we get 20 or 30k.
When it initially hits Steam, let's say then that it gets a big boom, and adds (being generous in all this), 40k.
So in a year, Blockland shoots up from roughly 40k up to 100~k.
With ID boundaries being broken through much quickly it'll be so much harder to take notice of what range is new. Sure, at the moment we can all say that the 30k range is the newest, but if you jump through the ranges quickly, it doesn't take long for you to lose track.
Now, let's say that we have this scenario, and the playerbase shoots up even as high as 100k.
And you claim veteran players will bully older players.
Well, if we consider older players at this moment to currently be anyone below 30k, so everyone from 0-29999, that's a small portion of the entire playerbase.
THose people, if they bully other players, they're not going to get away with it well, if the other 60% of the playerbase decides to just ignore them.
Also bare in mind that, as is default currently, one can't see BLID's of people by default.
How many people will miss this? There will be whole groups of people who have no idea what BLID's are and which are the newest. They're not going to care.
And if you get a massive burst in population all of a sudden, and all the 40k's appear, and barely any time later (in comparison to the rate of growth now), the 50k's appear.
Well, you're not gonna get the 40k's bullying the 50k's when they're still equally as new.
It won't be how the <10ks bullied the 10ks, and the 10ks bullied the 20ks, and the 20ks can bully the 30ks.
You honestly will not get so much ID Prejudice.
The entire concept of ID prejudice is sort of fake. In the same way that it's stupid to think all new players are dumb, it's stupid to think that all old players think all new players are dumb.
Anyway, that's an overstretched rant.
There won't be a problem with ID prejudice if there's a big increase in growth.
I don't have a real problem with it being on Steam.
Many games have Steam access without making it manditory. You could just as easily still purchase Blockland directly from blockland.us, and then play it from it's own launcher, without having to go near Steam.
The Steam access would just allow you to tap in to the steam community more. Advertise Blockland more, spread it further afield and generate more buzz for it, and make use of Steam Groups for Clan stuff, and use the Steam Workshop to promote modding for the game.
I'm being generous in my estimates above on how much the community would increase, but even it weren't as high, it would still be greater. And even if it doesn't sell massively, like many other smaller indie games on Steam, which get lost in it's massive database, Blockland will get annual increases in players. How many people went and bought new games on Steam that they had never heard of before, when it came out on the Steam Summer Sale or the Winter Sale?
And more players isn't a bad thing. Sure, they have to learn how to play the game, but who didn't?
It's not going to take them forever, and if they happen to be bad at it to begin with, it's not going to bother you. It's hardly going to obsctruct you. They can build on their own servers, or you can build on your own.
And more players, makes more servers, makes more ideas, more gamemodes, more creativity, more to do, more fun.