The two most popular social networking sites, Facebook and Twitter, are adding features to their Web sites in a bid to improve user experience and entrench their hold on the market.

Facebook plans to include the hashtag, a popular icon in Twitter, as a way to group conversations. The hashtag is a keyword or phrase preceded by the pound (#) symbol to collate Twitter messages into a single news event or topic.

For example, with the Wednesday election of Pope Francis, the hashtag #PopeFrancis was used.

By tapping the popular hashtag, Facebook hopes to allow members to easily pull up all posts about a similar topic or event quickly as index to feeds on trending topics which would encourage members to stay logged in longer and view more ads.

The foray of Facebook into Twitter icons is seen as part of the intense battle among social media sites for more mobile users and advertising income. Facebook, however, did not provide a timetable for the launch of the hashtag on its portal and declined to confirm or deny the report.

"We do not comment on rumor or speculation," Facebook said in a statement.

Meanwhile, Twitter provided on Thursday users the ability to view line breaks which could work for tweets that depict a conversation.

However, some Twitter members could abuse the feature that would appear like you are reading a Scrabble vertical entry. Tech experts warn the effect could be disastrous because Twitter, which counts more than 200 million users, has been known for simplicity defined by its 140-character limit.

Investorplace.com has noticed the tendency of Twitter to add new features in a bid to be more competitive with rival social networking sites, by warned constant changes could result in mass member defection like what happened to Friendster and MySpace.

"The change could undermine the very simplicity that draws people to Twitter instead of the fairly uniform feed users are accustomed to. Twitter is opening itself to more clutter, with the potential for tweets to look more like poems (in structure) than pithy messages. Moreover, it could interfere with tweets' easy compatibility with the scrolling ticker graphics at the bottom of news and sports broadcasts, like ESPN's BottomLine," commented InvestorPlace writer Tom Taulli.