The simple answer is No, it does not disrupt your SEO.
At Po.st, we have a feature called ShareURL, it helps track the actions of users that are copying your url's with the intent to share. After copying a url and pasting it somewhere, you may have noticed an extra parameter gets added to your URLs:
We've added this parameter as a way to track clicks on the shared URL to connect them with that specific share, without it you'll be unable to record this type of action. This added parameter DOES NOT affect your Search Engine Optimization efforts. Search engines are designed to identify these type of tracking parameters and remove them from their indexing results. A URL with the this added parameter looks the same to Search Engines as a URL without it.
Disabling tracking will prevent Po.st from being able to record any clicks that happen on shares. This means you will not be able to monitor the Virality of your shared content.
You can review the safety of this type of tracking and added parameter: http://po.st/GoogleSEOParameterBlog
You can read more about enabling URL copy paste tracking here: http://po.st/ShareURL
You can also read more about disabling all tracking here: http://po.st/DisableTracking