Applied on: Linux (Cpanel) Hosting
WordPress, since its inception on May 27, 2003 (It's already been 10 years?), has become the most common 'go to' blogging tool in existence. Staying within the timeline, come May 2004, we saw the introduction of the now so popular 'plugins'. With over 21,000 free plugins in the WordPress database, and a good portion becoming "paid" or "premium" (not to say they don't work without payment, just less functionality and options overall). From Facebook to Search Engine Optimization (SEO), there's a plugin for it.
These little chunks of code can be enhanced, updated, and if in the case of poorly written code, deactivated. You may be thinking, "Why would I ever deactivate this great looking piece of work for?" Well, it's simple: Compatibility, Resources, and Loading Speed. That little piece of code could be causing a Terms of Service (ToS) violation, and in turn causing your site to be taken down until properly fixed or discontinued.
Compatibility: the more plugins you have, there is more chance to have some of them causing problems. Always test plugins when adding new plugin, it is rare, but it can happen. I always have local copies of all my websites, and when new things are added, I always test locally before moving to live server.
Resources: the more plugins you have, the more server resources will be used. If you are on the shared hosting, I recommend that you review if you really need all plugins you might have already. Test different plugins you can use, because with too many of them active, you can easily hit the limits imposed by your hosting.
Loading Speed: more plugins = less speed. It is very important to use cache plugins to optimize front end loading, to minimize external files and use CDN to load external resources.
In short, make sure you keep that CPU usage down and minimize the plugins you really need, if you feel the need, the developers are usually readily available to assist you with any issues you have related to the plugin. If they're not, and the plugin hasn't been updated in over a year, stay away from it.