Merely an obviously useless thing.
I just noticed that the cabby, when he first appears (in the restaurant scene), in A Case in Pink, had the following licence plate : OVO4PYG.
Sheepishly believing (in spite of, well, the facts) that Moffat doesn't do anything random (and it's the pilot, and all that), I decided to interpret it. "4PYG" is obviously "for pig", so (plural aside) "for/to the cops". OVO now. Well, I would say, it's the acronym for October's Very Own. So Drake and his crew. Also, then, an obvious hint towards homosexuality in a militant form (that is, if you know who Drake is, and OVOXO).
Which would subtely suggest that Sherlock is a gay anarchist.
Or else, and that is a distinct possibility, I just need a girlfriend.