Unfortunately with that system when people change carriers they have to remember to notify you. (full disclosure: I work for Twilio but I have been trying different SMS techniques for years so this comment stems from that experience)
The email to SMS gateways are much slower in my experience than sending an actual SMS message through a quality service like OpenMarket.
Just like SendGrid might be in trouble, Twilio must also be wondering what the future will hold.
Would love to see someone from SendGrid and Twilio come here to explain the main differences and the cost/benefit of the two services.
I just started at Twilio two days ago so I don't have an answer for that but I'll see if I can track someone down that does.
At 3 cents a message, my freemium service would go bankrupt fast. Twilio has way overestimated the value they provide. My guess is that AWS will be much cheaper, like 100x - 1000x cheaper.
I thought the SMS problem was that the phone carriers apply higher fees to them?
Perhaps Twilio does pay the carriers, but I send hundreds of text messages a day and pay nothing because I send it through their email to SMS gateway.
I'm a long time HN user that just started at Twilio so I'd love to talk to you about your app. Can you email me at jsheehan@twilio.com if you want to talk more?