For the sake of compression, some of the characters that appear are composites of people I've known, and some events appear out of precise chronology.

Devices such as composite characters and shifting times to compress the narrative do not belong to the world of biography and autobiography.  Such books are expected to be as long as they need be to tell the author's entire story.  With a serious academic work, that can mean thick multiple volumes.

Narrative compression is used when adapting a book for the stage or in a film.  There it is both vital to hold the audience's attention and to keep the overall length within the capacity of the average bladder.  Readers can skip a section of a book they find uninteresting.  An audience falls asleep or exits the theater at intermission.  Thus, a writer adapting a book for a play or screenplay will combine salient parts of two or more characters or multiple episodes from the print source into composites in order to compress the narrative for dramatic effect.  A classic example is how the suspense novel Six Days of the Condor became Three Days of the Condor when adapted to film. 

The political left has a long history of using plays, movies, and TV series to push their agenda because dramatic media showcase their agenda items to good effect.  Many audience members get so wrapped up in the images, characters, and action that they don't stop to think about the huge dose of political propaganda being served on the side.  This is one reason why the left talks so much of narratives.  The political right, on the other hand, completely dominates the emotionally cooler medium of talk radio, where words alone have to carry the message.  On radio, one does not compress words for dramatic effect.  Words are amended or abridged to tighten arguments.  If the argument isn't cogent, the radio audience turns the dial. 

One could speculate that people on the political left have gotten so out of the habit of forming cogent arguments in favor of framing dramatic narratives that they were gobsmacked at how poorly their proposals fared during recent oral arguments at the Supreme Court.

The other genre where the technique of creating composite characters is used to great effect is historical fiction.  Many authors who have spun a series of tales began their works with research in their respective historical eras.  Real feats of heroism by different men are often combined and attributed to their fictional hero, creating, in effect, a composite character who manages to be everywhere and do almost everything.  Different branch of service, wrong regiment or division -- it makes no difference to the novelist, whose fictional hero always manages to be in the thick of things.  Herman Wouk's naval commander Pug Henry is in a British bomber in the first air raid over Berlin, experiences the German assault that falls just short of Moscow, gets sunk at Guadalcanal, plays bridge with Ike back in Britain just before D-Day, and then makes it back to the Pacific for Iwo Jima.  Bernard Cornwell's solder Richard Sharpe returns from duty in India on a British Man O' War that just happens to pass Cape Trafalgar on October 21, 1805.  Patrick O'Brian's Royal Navy Captain Jack Aubrey manages to squeeze at least six years of ocean voyages into five months in 1813.  Stephen Hunter finds that his latest story in the saga of Vietnam War sniper Bob Lee Swagger has to contradict events in an earlier book, or he has no story to tell.

Dreams from My Father has elements in common with the be-everywhere, do-everything bravura of the creations of historical novelists.  Incidents in Dreams often seem framed to make Obama seem special, even heroic to the target reader, a subset of urban elite opinion-makers obsessed with race.  Obama, the multiracial citizen of the world who spent his youth in Asia, chose to be a black man in an America this particular audience sees as perpetually and irredeemably racist.  That's almost as transgressive as dining on dog.

The idea behind Dreams was that when the time was right, the people for whom it was written could then sell Obama to the entertainment addicts in the general population who let others do their thinking.  If during this exercise most people Obama had encountered during his still-young life were turned into composite characters, incidents didn't add up, and the dates weren't accurate, those are all just facts that can be dismissed for the sake of overall narrative. 

Some novelists address their distortion of historic people, places, and events in an epilogue that is a mea culpa for messing with history.  A few even take some care to attribute the heroics they purloined back to the often obscure real-life heroes.  Obama addressed the issue of how he messed with history in the writing of  his autobiography in a preface which seems to have gone largely unread.  The difference is that the former seek merely to entertain, while Obama sought to mislead in the furtherance of his political ambitions.

Perhaps when Obama begins working on his next autobiography, he can introduce his former composite girlfriend to an important character from this phase of his life: Mr. Straw Man.