Whats interesting about this is that SV Angel invested. Ron Conway has a very close relationship with Twilio and The TwilioFund is "powered by 500Startups and SVAngel".
I wonder if they invested beyond the Start Fund
Yes, we invested beyond Start Fund. We often invest in "competitive" companies either in present or future. By that, I mean that we invest in companies that are competitive now or unrelated companies that for one reason or another, become competitive. In fact, it's more common for us to see companies that are competitive now diverge just in enough so the end products are not competitive.
We invest in founders, trends and spaces. We have a conflict policy that's based on what Ron has implemented over his 20 year career. I talked about our policy on Quora here: http://b.qr.ae/u8dZQ9.
Here, we are big fans of this trend - new voice services being created and disrupted by software. Thus if we like founders working on this problem, we will be positively inclined. We are huge fans of Jeff at Twilio. We are also big fans of Venky and his team.