Both Google GrandCentral and SocialShake.com are very unique and similar in nature to one another however they are both two completely different communication tools. GrandCentral is for phones and SocialShake is for email.
GrandCentral gives you ……

I did a search on eBay for Grand Central invites as well and you are correct that they’ve all disappeared. I checked my GC account and it appears Google has discontinued the new Grand Central member invite function - or at least I wasn’t able to locate the option setting to send out new GrandCentral invites.

My advice is to visit Grand Central’s main web page and submit a request to reserve a Grand Central phone number. As the site mentions, Grand Central is currently going through its Beta test phase (still after all these months) and will open up the system for new sign ups eventually. Not sure why the free telephone number program is still not publicly available.

I got my Grand Central invite a year ago via eBay when it first came out. Back then there were plenty of invites…now they seem to have become extinct.

I received an invite but the GC activation is not compatible with just a single landline. I got a phone number but couldn’t complete the activation. My email automatically scrolls off after a few weeks and I lost my invite, so I thought I’d buy one on ebay, where they are available for 99 cents. But PayPal would only let me send 20 cents (because I’m not Verified and I’m bumped up against their sending limit., so that didn’t work.

But then PayPal closed my account for inactivity. (Well, DUH, there was no way to use it if I could only send 20 cents.) So I called PP and they got me signed up again and I got Verified without the huge hassle I had previously.