Pandora, the online music streaming service, has laid off 20 of its 140 employees today, founder Tim Westergren announced in a blog post. The list of startups cutting staff and other costs in the face of mounting economic pressure is growing and few are immune to the challenges knocking on everyone’s door. Some are reacting swiftly on the front end to help soften the blows and absorb additional losses before the depths of this recession are even known. But worse yet for so many startups just getting off the ground is not knowing how much change is needed to plan for tough times ahead. “Letting go of an employee will, for me at least, always be the most gut-wrenching thing there is,” Westergren wrote. Still, there are positive signs the company can hold on to for the time being: the pending royalty rate resolution is moving along and its userbase is growing. No cuts were made to the company’s ad sales force and indeed it plans to hire more in that area.