No surprise here. Warner Bros. put the first nail in HD-DVD's coffin with the announcement at CES that WB hi-def content would thereafter only be published on Blu-Ray. Walmart, Best Buy and Netflix hammered in the final nails over the past week or so. When retail won't sell your product, it makes it very hard to stay in business.
To Toshiba's credit, it didn't waste time in seeing that the game was over and accepting defeat. Toshiba is a great company with excellent technological and business skills and history. Being a great company (especially in the technology industry) means having the flexibility to change when it's time to change.
I think Toshiba also recognizes that the entire disc business has a limited lifespan. Eventually (in the not too distant future) all content will come down the digitial pipeline at the push of a button. Everyone knows this. So, there was really no reason for Toshiba to keep fighting. Aside from the fact that they had no realistic chance to retain any significant market share, it's a business that they would have abandoned sooner or later anyway.