The general rule of thumb in the domaining world. Only buy a domain if you can see an easy route for development.
So, what to do with Greeting.me well, all I can say is this, if you are not 100% happy with or you can't find a fit consider the following, with every .me auction the one word dictionary domains are increasing in value. That does not look set to change yet.
I would say that if you hold out a few months and you relist this in the next .me auction, you will easily get your money back on it, and some.
I have maths.me that I bought a while back for about $100. Americans say math but UK and other english speaking countries like New Zealand say maths that is why I was attracted to it.
mathematics.me sold in this auction for $499 from my perspective maths.me is a stronger domain than mathmatics.me
I was thinking of developing my domain into a math/s tutor site, but I might just make a quick buck in the next .me auction.