Why don’t the big players accept OpenID as authentication mechanism, although some provide OpenID accounts? Kevin Farnham raises some valid points in this discussion:

So, what does it mean if we have a flurry of companies providing OpenIDs to users, but almost no one accepting OpenID credentials? Why would this happen? I can immediately think of one good reason: providing OpenID URLs is relatively easy to do and does not require a lot of coordination with other vendors; accepting OpenID credentials is a more complex process and requires interactions between your own servers and those of all OpenID providers. Providing OpenID sounds relatively safe compared with accepting it.

Being vulnerable to phishing attack, especially for non tech savvy user, OpenID is not suited to provide high security accounts. I personally think that until a solution to this problem the Protocol is facing some really hard times.

I think so. I think the news that so many people have OpenID URLs will encourage more sites and vendors to accept OpenID credentials. It will provide them with a way to stand out from the crowd. Maybe the big players won’t join in right away, but for smaller sites accepting OpenID has a lot of advantages

Providing their users with an easy way to register and use their services will certainly be a major advantage  for many smaller players. And some others are getting on the train too, remember the Digg announcement a few days ago?