agree with rocky, and with Eddie: if there's evidence that the prosecution was malicious, there's a case for releasing the complainant's name. But not otherwise.
This may seem unfair, but it is to tackle even greater unfairness: it is believed that there are 60,000-95,000 rapes a year (the figure is very vague) - but only 1000 convictions. (And a few of those convicted are just cautioned.)
This seems ludicrously low and suggests thousands of rapists are getting away with it. So defendants' names are released, often in the hope, as you say, that other victims of the same person will come forward, which would both give them a voice and demonstrate a pattern of offending.
But many people, including quite a few on AB, are convinced that all women are liars.
http://www.independent.co.uk/news/uk/crime/100000-assaults-1000-rapists-sentenced-shockingly-low-conviction-rates-revealed-8446058.html