Help! Some Beatles fans are feeling down about the latest use of a Fab Four song in a commercial — the 1967 peace anthem “All You Need Is Love” highlights a new disposable diaper campaign. “I just cannot see a Beatles song being used for trivial things … not Beatles songs!!!!” fan Andy Bonnell said by e-mail from Liverpool, England, the Beatles’ home base. Such sentiments represent something of a lost cause. A version of their song “Help!” was used in a car commercial in 1985, and the many appearances since then include the late John Lennon’s son Julian’s 2002 cover of “When I’m Sixty-Four” for insurer Allstate Corp. and current Target Corp. store commercials that use a version of “Hello Goodbye” — “Goodbuy” in the ads.