Microsoft News Center:

As other states recognize marriage equality, Washington’s employers are at a disadvantage if we cannot offer a similar, equitable and inclusive environment to our talented employees, our top recruits and their families. This legislation would put Washington employers on equal footing with employers in the six other states that already recognize the committed relationships of same-sex couples. Passing the bill would be good for our business and for the state’s economy.

Interesting that this support is couched in economic terms and not ethical or moral ones.