The fiscal sponsor must be a 501(c)(3) organization as recognized by the IRS. The fiscal sponsor cannot be an organization whose tax-exempt status is pending. The sponsored project must be able to qualify for exemption under section 501(c)(3), even if the project has no intention of ever applying for it.
Pressing the Ignore button on the listed invitation on the LinkedIn site is effectively a soft rejection. The message then moves to your Archived folder. You can later choose to open the message again and accept the request.
on facebook, people usually either accept or deny a friend request right away. well, i usually accept most of them when i first see it. guess they feel bad if they deny it but then they don't see you as a friend or don't want to get to know you so they don't accept the request either. The best thing to do (in their opinion) is to leave the request hanging so they don't have to deal with it.