Hi James:
I haven't given too much about the potential negative impact of ancillary copyright specifically in relation to Wikimedia projects, but there are major negative consequences for users, and businesses too.
Spain and Germany experimented with ancillary copyrights for press publishers, and both seem to have failed miserably [1]. The Spanish law ended in Google News shuttering its operation there because it would have been too costly to have to pay license fees to news publishers for snippets/links provided through their aggregation service. And surely this harmed users, who would then have a harder time finding the news and information they were looking for. Simultaneously, the publishers were shooting themselves in the foot because they eventually realized that Google News (and possibly other aggregators) was sending a huge amount of traffic their way (duh). But without it, traffic to the publishers' content went down. The same thing happened in Germany, except the German publishers saw what had happened in Spain and literally gave Google a free license to their content [2].
And it's not just the big news aggregators that are affected. Check out this story about a small business that curated links and news about alzheimer's disease that had to remodel their entire business because of the ancillary copyright law [3].
Even if the ancillary copyright for press publishers gets adopted, the benefits to authors are not at all clear. On the topic of remuneration: there's no evidence showing any connection between ancillary copyright for press publishers and increased income for authors, i.e. publishers have no incentive to redistribute any potential revenue back to authors. This is probably not shocking. And under this scheme, everyday users and consumers of news and articles would potentially face more constraints in quoting, linking to, aggregating, or otherwise using works protected by a new ancillary right for press publishers.
I hope this helps a bit!
timothy