I don't like the message Twitter sends with the semi-walled garden. Maybe I'm completely wrong here, but this to me says "develop on our platform and if you come up with a good idea and we like what you do we'll just do it ourselves"
Add to that the obviousness of this app, and bayesian chances are pretty high they just came up with it concurrently but were later with the release.
EDIT: It also explains why Twitter went so draconian on Meerkat.
EDIT2: But I'd have to add: yeah, Twitter's behavior is chilling. The way they cracked down on Meerkat, and now just try to play this launch off as if nothing happened, it's disingenuous. Just come out and say it, Twitter: you used your technically justified power over Meerkat to gain competitive advantage.
EDIT3: A friend tells me they didn't develop this app, they just bought it. Makes even more sense.
Periscope had been in a closed beta for months before they were purchased. I'm surprised no media has ever tried the angle of Meerkat being a Periscope clone.
Doesn't matter how much you invest, it's not the same drive.