Cobweb, fungus or something more serious?

cobweb or fungus?
Originally uploaded by modernemama

I noticed a new decoration to the siding yesterday, one I haven't seen before. It's 2-4" across and 3-4" long with a curved edge. There are groups of them under my bedroom window and along the east side of the house, on the garage.



Does anyone have any idea what they are? They'll be coming down this weekend when we are power-washing, but I'd like to know if I should add it to the list of things that could potentially cause my house to fall down and thus I should worry about. Thanks.