Reuters: President Barack Obama on Friday slammed the companies involved in a massive Gulf of Mexico oil spill as BP Plc readied a siphoning system to contain a growing environmental disaster. Obama applied further pressure on the companies involved in the unfolding drama, criticizing them for a "ridiculous spectacle" of publicly trading blame over the accident in his sternest comments yet on the situation. With oil gushing unchecked from a blown-out well a mile under the Gulf of …