WordPress.com is a free blogging platform great for starting a personal blog to share your thoughts about something. However, staying in WordPress.com for long won’t do you any good particularly if you want to earn revenue from your blog. WordPress is a free account that does not offer extensive customization, does not allow ads, does not allow video uploads and your blog is suffixed to WordPress.com. Getting a web host nowadays is pretty cheap. You can get one for as low as $3.5 per month but the revenue you’ll get from ads can get to hundreds of dollars per month. It also has freebies like Google Adwords credits, and you’ll get to host unlimited number of websites plus get your own email account. However, choosing a web host is crucial for the success of your blog.
This article will explain why you need to pay for a web host rather than stay at WordPress.com: http://skyje.com/choosing-web-host-wordpress/