I made the following observation: Just after publishing a link on Twitter, there are several accesses from different IPv4 addresses on that URL. Since I published a link to one of my own servers, I saw these connections on the firewall as well as on the server itself. They all called the http website and stayed for 2-3 seconds on that page.
I would have expected a few search engine bots, but most of the reverse lookup resolutions led to unknown or meaningless names. Maybe someone out there made the same observation with more details on that? Who is accessing the links? Automated bots from Twitter itself? Search engines? Malware bots searching for new victims? ;) And over which function do these hosts know, that someone has published a new link?