Do I really need Bonjour on Windows?
From Apple's knowledge base article about Bonjour on Windows (my emphasis):


  
  iTunes uses Bonjour to find shared music libraries, to find AirPort Express devices for streaming music to, and to find Apple TVs.
  Safari uses Bonjour to find devices advertising web pages on your network. Many of today's network printers, network cameras, and wireless gateways provide a web interface for status and configuration, and many of these devices (especially network printers) now advertise those web pages using Bonjour, to make them easily discoverable in Safari.
  Internet Explorer, via the Bonjour toolbar plugin, also provides easy discovery of Bonjour-advertised web pages.
  The Bonjour Printer Setup Wizard uses Bonjour to discover and set up Bonjour-advertised network printers.
  Adobe's Creative Suite 3 applications use Bonjour to discover digital asset management services.
  


If you don't use any features, then removing Bonjour won't cause you any trouble (except perhaps Apple Software Update might offer to install it again...)

Furthermore, this page has some instructions for more throughly uninstalling Bonjour.