As further evidence of the cloud movement, cloud communications company Twilio has raised a $17 million Series C round of funding from returning investors Bessemer Venture Partners and Union Square Ventures, according to media reports. In total, Twilio has now raised $31.5 million, according to CNET.

The San Francisco-based company makes web-service APIs so developers can build their own scalable, reliable communications applications for voice and SMS. Twilio has grown from 25 employees to nearly 100 in 2011, company officials said in this blog post.

This year, the company grew its customer base by 400 percent to nearly 75,000 developers, expanded its offering overseas to Europe, and expanded its product line dramatically with the introduction of SMS Short Codes, Twilio Client and Twilio Connect, according to a company statement released Dec. 7.

The cloud-based infrastructure web service that breaks down this complex field into “building blocks” that developers can use to integrate phone calls, text messages, and IP voice communications into their web, mobile and traditional phone applications. No contracts or upfront fees are required.

According to Digital Media Wire, the company’s approach has been characterized by CEO and Co-Founder Jeff Lawson as “drawing an owl” – “shorthand for the company’s philosophy that simplifying the first steps of a complicated challenge encourages people to take it from there and frees their creativity,” the report said.

“At Twilio, we’re opening the black box of telecom to developers and companies that can now innovate in this previously esoteric field,” Lawson said in a statement. “With this new round of funding, we look forward to expanding that mission.”

Twilio, which is based in San Francisco, opened a London office and began its United Kingdom operations in October, the first step of an expansion plan that includes 20 countries in Europe and Scandinavia.

Bessemer Venture Partners and Union Square Ventures were also investors in Twilio’s Series B round, which closed in December 2009.  Bessemer is a longtime investor in SaaS and voice, having backed companies including Skype, VeriSign and Cornerstone OnDemand, according to Twilio officials.

Twilio is hiring positions in sales, marketing, and engineering. Interested candidates should visit http://twilio.com/jobs