There are very few things that can tank conversions the way misused ghost buttons can.
For the unfamiliar, ghost buttons are the barely-readable-by-default buttons that become readable once a person hovers over them, usually found in all types of agencies (including design/UX firms!) or just about any website whose need for pizzazz has somehow overridden every other goal the website has.
All right, that was a tad harsh. Companies can actually use ghost buttons as a secondary button when they want a more sales-oriented button to pop.
If a brand is using a ghost button as the main call-to-action on the page because it fits with their hip design, however, just remember that it's called a ghost button for a reason. If designers want ghost-level click-throughs, this is the right tool for the job.
This is an even more potent conversion killer when paired with auto-play videos on the homepage, or large images that leave no room for navigation elements.