Yeah, swusc's point is extremely important & hopefully Hagstrom mentions this as well. All this stuff is jam-packed with land mines.
The current 30 year rate would give a P/E of 20x for a company with steady earnings. In reality nobody wants to pay that much for anything but treasuries, because they feel that the payments may not actually arrive. So folks talk about a P/E of 10x or 14x or something for companies whose earnings might reasonably be expected to continue without growing or shrinking.
Opinion: To help make all this more incomprehensible, people also use the phrase "discounted cash flow analysis" to mean "we ran lots of spreadsheets before we picked a PE".