There are lots of ways to lose your 501c3 status. Here's one (with more to come):
* If outside donations don't reach 33% of your total: In our first year, all of our donations to run the sanctuary came from ourselves. When an IRS agent noticed this, she alerted us that 33 percent of our donations must come from outside sources within five years or we can lose our 501c3 status and become a "private foundation".