Both reddit and twitter have been extremely unprofitable for a long time. The only reason they were allowed to run for so long without making a profit is because investors were willing to bleed money in the hopes that they would be able to make money eventually.
When websites got killed by bad monetization ideas replacements were again available only because of those investors (like the digg->reddit migration).
Overall it's going to be harder for new ones to pop up, and if they are they're going to have those same monetiation schemes.
When websites got killed by bad monetization ideas replacements were again available only because of those investors (like the digg->reddit migration).
Overall it's going to be harder for new ones to pop up, and if they are they're going to have those same monetiation schemes.