According to this article, Steve Ballmer threatened to move more Microsoft jobs offshore if US tax rates increase. The article has how Microsoft tax dodges anyway by transferring their technology through Irish subsidiaries.

I know it is intended as a political threat, but moving jobs offshore isn't an issue. Many of the Bay area companies have great difficulty competing with the likes of Google for talented tech people and as a consequence they end up paying a lot for less talent. The result is that Bay area companies open up near shoring operations in cities like Phoenix, Portland, Denver, Salt Lake City and Texas.

I am sure Washington area software companies have a great deal of trouble competing with Microsoft for talented technologists and software engineers. Microsoft sending more of their labor overseas will only open up the market to Washington area software companies.

Another issue is that what companies can send overseas, they will, and in most cases have done already anyway. The arguments become if it is worthwhile or not, not arguments over whether to do it or not. So as a threat it is really not, though I am sure some nationalist politicians who don't have libertarian economic streaks in them will quiver in their boots at the threat.