Hewlett-Packard Co will become the largest company to hold an online-only annual shareholder meeting this March, joining a trend toward virtual conferences that some activists worry keeps CEOs off the hotseat. The Silicon Valley technology giant announced in a Feb. 2 securities filing that its March 18 shareholder meeting will be online only, a move that follows in the footsteps of dozens of other companies including Sprint Corp and Martha Stewart Living Omnimedia Inc. HP spokeswoman Sarah Pompei said the new format is cheaper, and will allow for "increased stockholder attendance and participation."