People regularly express surprise that Twitter is free, but it isn’t for everyone — Twitter Blue debuted in various regions last year, adding a few more features for those willing to pay $2.99 per month. The service informed members today that it is raising the price to $4.99 per month in the United States. That is unlikely to break the bank of information junkies who choose to pay for a service that still contains adverts in their feed, but it may be enough to make users wonder whether it is worthwhile.