My feeling is, to use a cliché, water does pass under the bridge, for a reason.
I can only speak for myself but tenuous work related frindships and online activity, like messages and emails, can start to become overwhelming. I used to share emails with a friend who lived over 100 miles away. We'd known each other as children but then life took us in different directions and we lost touch. We found each other again via Facebook and then emailed each other and met several times. She was as lovely as ever and we got on well, but this old friend was one of many who by now had started using emails to get in touch.
It hit me a while ago that I was spending so much time writing to so many people about different things. We had in reality become estranged and didn't share experiences any more, and online activity almost artificially kept alive something that would have fizzled out of its on accord after a while - had it not been for messages and emails.
I now have a policy of refusing to connect via Facebook etc to people who left my life a long time ago. Just because we have computers doesn't mean we have to be overjoyed to connect again when we probably don't have as much in common anymore and are unlikely to meet often, if at all.
Having too many friends (online ones) to keep corresponding with can be very time consuming. I slowly stopped replying to several as it almost seemed like forced correspondence. I didn't need to know the minutiae of their lives and they probably had little interest in my wittering about my grandchildren, book club lunch or holiday in Scotland.
The theory is lovely, the reality is time consuming and a bit forced. I hope that doesn't sound mean-spirited. I am trying to be realistic.