Shortly after departure, the pilot observed fuel coming from the fuel tank vent and elected to make a precautionary landing. He touched down in the first 1/3 of runway 17 at a speed of about 80 mph. The pilot stated that the brakes failed during the roll-out and he steered the aircraft off the left side of the runway to avoid a drop-off beyond the end of the runway. Before stopping, the aircraft collided with trees. After exiting the aircraft, the pilot noted an apparent 10 kt tail wind. He stated that before landing, the wind sock indicated a crosswind. The windsock was located in a sheltered area and the runway was lined with 50 to 60 ft trees on both sides. A check of the brakes revealed that they operated normally and had normal wear. An examination of the fuel system revealed that the left wing bladder had pulled loose from its attachments and had collapsed.