Absolutely not! We make sure that we behave just like you'd expect - in the background - while preserving your websites search engine optimization.
We do this through the use of Canonical Headers, essentially identifiers that tell Google and other search engines to not recognize http://snip.ly/abc as the writer and owner of the content. Rather, we forward all of the credit to the snipped site.
For example, if you snip example.com, the sniply link might look something like http://snip.ly/abc. When Google visits http://snip.ly/abc it doesn't give credit to sniply for any links or SEO, instead it gives all of the credit to example.com and effectively ignores sniply's presence.
The end result is that you keep all your hard-earned SEO!
NOTE: If you're interested in how we do this on a technical level, we use rel="canonical" link HTTP Headers. Google details how they work on their blog - http://googlewebmastercentral.blogspot.ca/2011/06/supporting-relcanonical-http-headers.html