Your reputation as a scholar is critical. It can be damaged by publication of papers in journals or conferences that are not reputable.
ABC’s Background Briefing on OMICS revealed hundreds of Australian researchers had been scammed by one single (possibly the biggest) predatory publisher. The article notes:
One of the biggest players in the sector is OMICS. Based in India, the group say it publishes over 700 peer reviewed journals. But Background Briefing has discovered that half of them are defunct, and the rest are suffering a credibility problem.
We counted over 200 Australian academics on their editorial boards. But it's unclear how many of them—if any at all—do any work for OMICS.
For example, Melbourne University academic Associate Professor Adam Bryant is named as the editor in chief of an OMICS journal, but didn't know about it until we told him.