Relevanssi and Sociable don't mix perfectly. If one enables custom excerpts from Relevanssi and uses Sociable buttons in search results, the results aren't perfect. I have received reports of blank screens. When I tried it, it worked, but the results look a bit funny, as the text Sociable adds to the end of the excerpt appears twice.
So, if you're using Relevanssi and Sociable, my recommendation would be to disable Sociable on search results (the option isn't on by default, either).