It's a fact that people leave treasures on the sidewalk, expecting them to be taken to the dump by sanitation engineers only to find that other people pick them up and love them. It's probably been that way for a long time, too; otherwise we wouldn't have that saying about one man's trash. But why Thursday, particularly? Secret sources tell us that folks want to get rid of stuff before the weekend. Because it isn't the weekend, though, passers-by are fewer, and the pickings are better. Also, upscale neighborhoods like Noe Valley yield high-quality items -- no one wants to be seen going through the neighbors' garbage. However, these same sources also say things like "I don't know! It's just true! Stop asking me!" and claim that the Mission's just as interesting. Would-be free furniture, clothing, and household-goods owners should probably just look in the trash every night. But it is true: Thursday's the best.