Indonesia shot past the United Kingdom to become the second largest Facebook market after the United States, reports market research firm InsideFacebook. The number of Facebook users in Indonesia has jumped from 25.7 million in June 2010 to 29.4 million as of last week and has gained nearly 500 thousand since then.

The main growth engine for Facebook’s expansion in Indonesia seems to be the youth demographic between the 18-25 age group. In Indonesia, more than 45% of Facebook users belong to this age group, way higher than the global average of 32%.

Indonesia is definitely the one of the most active countries on social media by virtue of its Twitter and Facebook rankings. Indonesia ranks third on Twitter and has over 3.2 million blogs.

Across South East Asia, Indonesia, The Philippines and Malaysia made the top 20 list of countries with the most gains in the number of Facebook users in the last month according to Facebakers, another site devoted to monitoring Facebook statistics.

Facebook has been witnessing strong growth in other Asian countries and its total number of users in Asia has exceeded the 100 million mark, according to Grey Review.  The United States is still in the leading position with over 140 million users.