Advantages:
- It’s free
- Fast to setup
- Easy to learn
- Lots of plugins and templates available so you don’t need to be a PHP guru or designer to have a nice looking site with lots of features.
- Easy to modify page templates allowing you to customize the presentation layers to your heart content
- Large and active open source community community of people developing add-ons, plugins, themes frequently
- Easy to host with simple requirements
Disadvantages:
- Many of the themes have a tendency to look the same or similar.
- PHP’s track record for security is pretty bad.
- Database queries may be very heavy
- It isn’t a full CMS product – which is fine for a lot of sites – but if your site is moving a long way away from something based around a blog then you might find it starts to creak a bit!
http://www.linkedin.com/answers/technology/web-development/TCH_WDD/308438-15378406