In June, as engineer Anselm Baird-Smith mulled leaving eBay Inc. for another job, he received a call from Google Inc. Within days, Google executives had interviewed him and dangled before him an enticing offer: a six-figure salary and restricted stock then valued at several million dollars, to be distributed over several years.

"Google was really aggressive and they moved fast," says Mr. Baird-Smith, who holds a doctorate in computer science and is known for his work as the developer of Jigsaw, software used in computer servers....