Does this bother you? Aggressively targeting your competitor's employees? Imagine if Google went to your startup and offered everyone 100K signing bonus to leave. Would this be OK, within the bounds of acceptable competition?
Even if I know that the company making the offer has such plans I'm still in a nasty tragedy of the commons with my coworkers.
If memory serves HN was very angry, saying it was collusion to keep developer salaries below true market value.
[1] http://www.justice.gov/opa/pr/2010/September/10-at-1076.html
[2] http://www.macworld.com.au/news/apple-and-google-face-salary...