There are several options when you need to either get to or get home from the airport, but none of them are perfect.
Getting a ride to the airport from family or friends is not always possible; taking a shuttle which stops at 5 other locations before dropping you off is annoying and time consuming; self parking your own car can be worrysome or expensive depending on where you decide to park (I was once at a self park at LAX and they returned the WRONG car to the man ahead of me!); taking a limo is a great way to go but it can be expensive and let's face it, a limo for one takes up a large carbon footprint.
What is a better alternative? You can share a ride and self park at a good facility like 105 Airport Park which offers valet and luggage service. Or try Hitchsters; it's a free car and ride sharing service for the Manhattan and San Francisco airports that matches you up based on flight times. You can even choose a gender preference or requirement (i.e. you can specify that the match MUST be a specific gender or no match). Their philosophy is that every time you take a cab you are sharing it with a stranger anyway (the cab driver), so why not share it with two strangers and save some money by splitting the cab fare?
They are a new concept and company, so the more they get people to use their service, the more they will expand to other cities; give them a try next time you are in NY or SF so that they can expand to LA and a city near you.