I always put facebook and twitter on my websites. Regardless of what niche they are, you can always get a boost in traffic through these two networks.
You should use social button. if you are thinking that it will increase the page size. js or css then its correct they do this to pages. but you can use static buttons if you don't wana increase you page size.. but now days its mandatory to use social button to get success.
Yes, you can use because these buttons are getting promotion of your website so at this time approx all websites are placed these buttons on his home page. Getting these cod is too easy through internet and place in your home page.
this is also a kind of marketing your site via social networking sites. Apart from Fb and twitter, now a days Google+ is also most commonly used widget to increase the visitors count to your site. Good Luck, Rizecorp