Having access to your template is important

Without access to your template, you can't make the changes you need to make. Total control over everything that appears in your blog is extremely important.

Having said that, whenever you add something new to your blog, make sure it fits. Don't just add because it's 'cool'. Or for that matter, don't just don't add simply because everyone else has it. You want your blog to stand out from the crowd. While it's fun to get the 'new thing', it gets wearing to everyone else who comes to your site and sees the same thing everyone else has.