I'm thinking about running a bitcoind full node to help out the bitcoin network.
Would it be feasible to run a full node through one of the new macbooks?
(12", 250GB HD, 8GB RAM, 1.1 GHz Intel Core M processor)
It's certainly possible. I used to run a full bitcoind node on a 5 year old MacBook Air. I stopped (and moved it to a larger machine) because the size of the blockchain database was becoming annoying - it's currently 52 GB and always gets bigger. If you can spare the space, there's no problem with actually doing it.
You sure can. The trickiest part is the initial download of the full blockchain. It will take about ~4 days. It might be 52Gb but doing a Get Info will show 64Gb. You've got heaps of space though.
Hopefully you've seen: https://bitcoin.org/en/full-node#mac-os-x-yosemite-1010x and you'll want to enable incoming connections: https://bitcoin.org/en/full-node#enabling-connections
Then you should see yourself on this map here: https://bitnodes.21.co/#join-the-network once you're up and running.