Twitter apparently is on an acquisition spree – with its most recent purchase, the second one this month, being the mobile messaging company Cloudhopper, which essentially specializes in mass texting campaigns for advertisements as well as promotion of products.

Though there has been no official disclosure about the Twitter-Cloudhopper deal, the microblogging site Twitter said that Cloudhopper allows it to connect directly to mobile carrier networks in countries all round the world.

Founded in 2008 by Joe Lauer, Cloudhopper claims to have patent pending technology that “supplies the underlying software and infrastructure to reliably scale and geographically disperse some of the world's highest volume messaging programs -- all with zero downtime.”

Meanwhile, with an official Twitter blog post recently noting that the company “processes close to a billion SMS tweets per month,” SMS is apparently the key growth opportunity for the company.

Twitter co-founder Biz Stone said at this year’s Las Vegas CTIA trade show: “There are over four billion mobile phone accounts in the world, all essentially Twitter-ready. Compare that to only about two billion PCs. So it creates a huge growth opportunity for us.”

Already, Twitter SMS is available in from all leading operators in Canada; from mobile operator Bharti Airtel in India; from O2 in the UK; from Vodafone in New Zealand; from Telstra in Australia; and from AXIS in Indonesia.