With AT&T, the pricing for unlimited plus lines is as follows:

 1  line: $90/month
 2 lines: $145/month
10 lines: $310/month

Each additional line after the 2nd is $20, so at 10 lines the average cost per line is $31/month.

I'd like to get 9 friends together to take advantage of this. It would be a 66% discount over individual plans, and save each participant $720 dollars per year.

However, the more administration that I have to do, the less it would be worth it for me to organize this thing, so there would be some pretty restrictive caveats:

1. Since getting and tracking payment from 9 people every month would be a huge time sink, I would collect 6 months of payment up front. This means a flat payment of $186 every six months, payable via paypal or bitcoin.

2. I wouldn't allow porting numbers in or out. This is probably the most restrictive caveat. The way that you could make this work if you want to keep your number is to port your current number to google voice. On android, making calls and texting via google voice is seamless, and additionally lets you make calls and text, and check your voice mail from a browser. On iOS you have to go through the Google Voice app, but it's definitely doable.

3. No refunds! However, the savings are so significant that if you pay the ~$186 and go back to an individual plan after 2 months, you would only be out $6.

4. Although pricing per-line is fixed, I can't predict what fees or taxes will be levied. When I receive the first bill, I'll divide the total by 10, and ask for the difference between that and the $31 paid up front. I expect this to be less than $5 per month or so, but I have no idea.

5. I would place blocks on all the lines for anything that might incur an additional charge. This means no international calls, no international roaming, no premium texts, no premium numbers.

6. Since there are no contracts with AT&T, the prices could go up, at which point I might have to charge people more money or disband the clump.

7. At 5 months into the 6 month period, I'll ask everyone if they want to renew, and if so collect payment for the next 6 month period.

8. Should you decide not to renew at the end of a 6 month period, you would need to send your sim card back to me, either in person or via post.

9. You would not have administrative access to the account. This means that, in case of a problem, you have to go through me instead of being able to call customer service. This is mainly a security issue. If anyone is using their phone for 2 factor authentication, or as a recovery option for accounts, this means that they only have to trust me, and not the other 8 people on the plan.

10. Barring any unforseen complications which would force me to stop, I would promise to run this thing for two 6 month periods. At the end of the second period, if it turns out to have been too much of a pain in the ass, I reserve the right to stop running the plan, and cancel the other 9 lines. I sincerely hope that it isn't too annoying, and to run it for as long as it saves money, so hopefully it doesn't come to this.

I haven't fully decided whether this is a good idea or not. If you're interested, or have concerns or questions, do let me know in the facebook thread!