No, I've never had Prime and I just started my 3rd year in Vine in July.

I've been a prime member in the past, but after a few months of not being in prime, I got invited so no I dont think that matters at all:)

I've never paid for it but have used the trial periods a few times.

No.  I've heard that invites are random.  Can't confirm.  Can't deny.

I'm not a Prime member, never have been. It was mentioned in my invitation that it was because of my history of previous reviews on Amazon that I was invited to join.

prime membership isn't required. I don't think anyone on here really knows if there is anything one can do to increase the chances of an invite, but I suspect those who do a lot of business with Amazon may be a factor.

Out of pure curiosity, Im wondering whether or not invites get sent to avid reviewers without prime accounts. Has anyone received an invite without a prime account? 

A colleague of mine and I both received invites a few months back, but were both Prime members. Upon discussion today we discovered this. Are invites only sent to prime members?

Question: To be invited, do you have to be an existing prime member?