I'm the author of this blog post. And I don't think the invitation was the main issue here. I did have a ticket, and I wasn't visiting any friends there who could invite me. Also I haven't been asked about the invitation letter during the main interview, I haven't even been asked why I don't have it or anything like that...
I think the main issue was my not permanent employment, here, in the UK. I just don't like the way the officer was interviewing me.
I think Twitter bought Periscope (In January Sometime) before Meerkat launched (Early March), but Twitter didn't disclose the acquisition until after Meerkat launched (Mid March).
I'm happy for them. Don't get me wrong, I love meerkat, it's a great app. Periscope looks like a one night hack for me. My point is that their entire app relies entirely on Twitter.
I think the main issue was my not permanent employment, here, in the UK. I just don't like the way the officer was interviewing me.