Update 3:07PM 9/17: Found out why invitations aren't on eBay and probably won't be- unlike Google which restricted invitations to just a few per beta user, apparently Yahoo Mash beta users can send out unlimited invitations...
Yahoo has announced a beta launch of their new social networking service to compete with Facebook, MySpace, Pownce, etc. (oh goody, another one!). I can understand why Yahoo wants to get into the social networking game, and to those who say the world doesn't need another site like this (myself included), you might be right but don't forget how late Google got into the email game with their Gmail service. When they did, many were singing the same tune about not needing a new email service. Yet Google has done very well with Gmail. So I get why Yahoo wants to enter the social networking game, especially considering they already have millions of registered Yahoo users they can provide with a free account.
What is interesting about Yahoo's service though is that just like with Gmail, the beta is invitation only, meaning you have to know somebody to get an account. But Google launched their beta with much anticipation and buzz from users who coveted an account, so much so that accounts were being sold for over $100.00 each on eBay. The Yahoo Mash beta has only been open a very short period of time, but as of today no accounts are being auctioned off on eBay at all. Simply put, the hype for Mash is nowhere near what is was for Google's Gmail launch.
We'll see where Mash is in a few months before we judge it though (we haven't yet secured a beta account, but if we do we will discuss it some more here).