You don't see large brands sabotaging their online marketing efforts. Messages are carefully vetted in order to preserve the brand image. Small business owners aren't nearly as careful about this, but it might be in their best interests do pay more attention to what they post online. Here are some thoughts.
Posting information that is demonstrably false or, at the very least can't be proven true will lead some people to question your judgement. After all, if you're not aware you're spreading lies, what else don't you know? Your credibility is one of your most valuable personal and business assets. You should be jealously protecting it.
Business is built on connections and a perception of shared values and trust. Posting information that's not true will lead people to trust you less. Every message you post has the potential to weaken or break the connections you've made with the people who choose to spend their time and money interacting with your business.
Small business owners are more connected with their customers and communities than big brand stores. If your personal social media presence is available to your customers and prospects, you may want to keep in mind the potential downsides posting erroneous information can bring. While nobody expects perfection, a simple fact-check before posting / re-posting / sharing a meme / infographic / statistic can be a serious credibility saver.
As a small business owner, you have enough issues to worry about. Lazy posting on social media can have unintended consequences for you when the information you're sharing is wrong, either by accident or design. Just remember: whatever you post is a reflection of you, which is in turn a reflection of your business. Accuracy matters.