Rachel Peridot Katz, senior analyst at the Global Philanthropy Group, a California-based consulting firm that works regularly with celebrities and luxury brands, says nonprofits must be savvy about which social-media influencers they engage. The ephemeral nature of some new platforms like Snapchat has only accelerated the cycle of fame. Audiences move on quicker than ever, she says.

"I think what the challenge for nonprofits is is being able to ferret out who has staying power and who is worth putting the time and energy into," Ms. Katz says.

How to initiate contact with these individuals varies dramatically, Ms. Teschler, Ms. Katz and others say. Many of the biggest stars now have agents and publicists who should be the first point of contact. Others have no representation and can be contacted directly through their social-media accounts.

This article originally appeared in The Chronicle Of Philanthropy