3 are from search engines. The other 80 are from corporate tracking this site.
In reality, when a forum says that there are X users online, it doesn't mean that they are online right that minute. In the backend forum settings there is an option to set how long a user (or bot) is listed as online after they left the site. It can be several hours even. In any event there are a shit ton of search engines that send a ridiculous amount of bots all over the net constantly. The Russian and Chinese search engines are really agressive with that shit. Google isn't much better. When I ran a forum, the search engines were always sniffing around. I ended up blocking the Russians and Chinese because it was a local forum and they were killing me with their bandwidth usage. No, a Russian search engine doesn't need to know what is happening on a small Midwestern forum 24/7 so get your 20 bot at a time barrage out of here.