If the company didn't have operational reserves for that kind of rough patch I'd be pretty worried anyway - but I'd probably consider it, yeah. A lot of that would depend on my situation at the time though - if it meant defaulting on my mortgage, then no, it's not happening. I agree it's perfectly fine to make a choice like that.
I agree, it's not reasonable to expect loyalty in either direction. I think the key for employers is to remove as many reasons for leaving as possible; then who cares if employees stay out of loyalty or out of logic, they're still staying.
edit: typo