A social marketing company Semiocast has revealed that Twitter has crossed the 500 million-user mark in June. Semiocast has also stated that out of those 500 million users, 140 million users were from U.S. alone. Brazil took the second spot with over 40 million Twitter users.

Twitter was expected to reach the half-billion mark in February 2012, but as the month and others passed by, the company did not say anything about it. One basic problem that most have found in reporting Twitter users is spam accounts that are created easily and frequently.

Semiocast has kept a track of Twitter users and the report seems fair because the company has received and analyzed tweets from most of the accounts.

In its report Semiocast has listed names of top 20 countries with a maximum number of users; with U.S. and Brazil taking the first and second spot, Japan coming third, while UK and Indonesia spotted at fourth and fifth spot respectively.

Not only countries, Semiocast has also mentioned that maximum number of tweets were received from Jakarta, Indonesia. Tokyo, London, and Sao Paulo came second, third, and fourth, as per the report.

A surprising revelation came by number 10 spot which was taken by Riyadh, Saudi Arabia. This leaves clear indications that Twitter is still gaining popularity. But what came as a shock is that the birth place of Twitter, San Francisco only accounts for .2 percent of tweets.