So you do a quick image search for logos or icons of said networks, and paste them on your website mockup or physical product.
(This process is no doubt how Ollie, the Twitterrific bird, ends up on websites to be synonymous with Twitter.)
Allow me to let you in on a little secret: all of these brands have web pages for you to download their actual logos. Hurrah!
This is probably the biggest of my pet peeves — incorrect logos. Louie is generous and links to where one can download the actual logos for several services. Definitely bookmarked for later.