I remember back in high school then university about writing essays and how you needed to have footnotes referencing your sources. But it was in University where the quality and integrity/reputation of your sources really reflected on the quality of your position paper and the grade you got.
Nowadays, sharing, linking, or retweeting something are your footnotes to your position paper/post. The quality and reputation of that source material then reflects on the strength of your position. Link direct sources and sources with a solid reputation and your position is strong. Link sources with a poor reputation or no reputation at all and you position is weak.