Some companies raise money even if they don't really need it. Case in point, Evernote has over $10m/year in revenue and a lot of their venture capital still in the bank, yet they decided to go for a big round of $20mil for a total of almost $30mil. They want to expand. The same is true for Twitter.

Whether the model works out for them or not is yet to be seen, but I don't think the majority of the people care enough about the bugs and uptime problems to the extent they will leave the platform or come back less.