HubSpot, a Boston based start-up, is on a roll to conquest the Long Tail of small and medium–size businesses to digital marketing, and help them convert visitors into leads and sales.

The founders, Brian Halligan and Dharmesh Shah, recently published a book, not surprisingly titled Inbound Marketing: Get Found In Google, Blogs, and Social Media, which spells out the basic techniques to make the Internet an efficient business driver. As with HubSpot itself, the book’s innovative nature is not to be found in new or unheard of marketing principles, but in its attempt to empower everyone with the right knowledge. And since knowledge is power only when applied, the Inbound Marketing book is all about execution. Just as a text book, the book break inbound marketing up into 4 fundamental parts: decide who you are and why your story is remarkable, get found, convert, analyze & repeat. Examples and to-dos aim at making the reading easy and actionable.

There is a chapter though, that you won’t find in this book: mobile. Why should mobile be part of an Inbound Marketing strategy? Consider these mind-blowing statics.

Did You Know That

• There will be 4.6 billion mobile users world-wide by the end of the year  (expected to become 5.9 billion by 2013)? 4.6 billion users: that’s 18% bigger than radio, twice the size of unique holders of bank accounts, 2.5x bigger than unique holders of credit cards; over 2.7x bigger than all internet users. There are 3 times more mobile phone subscribers than all TV sets on the planet. There are almost 4x more mobile phone subscriptions than fixed landlines globally, and more than 4x more mobile phones than all personal computers in use on the planet.
• There are 270 million mobile subscribers in the US and 4 billion text messages are sent each day? And Smartphones account already for 40 millions phones in the US?
• One out of every eight minutes of media consumptions happens on mobile?
• Mobile advertising will soon be a $3.1 billion dollars business, with search taking the lion’s share?

And did you know that Inbound Marketing Channels are already Mobile?

• Twitter is adding geo-location to Tweets. But a  few TwitterVille stories have already proved the power of this platform when used for mobile marketing:
  • Coffee Groundz, a Houston java joint, increased its sales 20-30% and was able to steal share from the nearby Starbucks by simply adding Twitter to its marketing mix.
  • The Roger Smith Hotel in New York City estimates an increase of $15k to $20k in sales through Twitter promotions this year.
• Mobile is Social- Social Networks are already the top Mobile Internet destinations world-wide.
• Facebook is heavily into Mobile
  • There are more than 65 million active users currently accessing Facebook through their mobile devices.
  • People that use Facebook on their mobile devices are almost 50% more active on Facebook than non-mobile users.
  • There are more than 180 mobile operators in 60 countries working to deploy and promote Facebook mobile products
  • Facebook Connect is also spreading out its tentacles on mobile.
• Consumers are falling in love with Location-based networks.
  • FourSquare has already 60,000 rabid fans, after 6 months from launch and zero advertising, all checking-in and happily promoting  their favorite venues? Loopt is following and expect more such stories in 2010.

Finally, did you know that consumers are asking for more mobile marketing? According to a survey conducted by mobile marketing agency HipCricket:

• 85% of respondents agree that the mobile web is a valuable source for information that interests them.
• 21% of respondents access the mobile Web at least once per day and 37 percent access it at least once per week
• 41% of respondents have visited a retailer’s website from their mobile phone.
• The most popular reasons for visits to retailer websites are to find store locations (70%), to find store hours (51%), to get directions (39%) and to look for coupons/promotions (29%).

Used for branding, for proximity marketing, for search, for engaging users in relevant conversations, as a sales channel and for payment, mobile is here to stay and I bet the next updated edition of the Inbound Marketing book will come with a chapter on Mobile and it will be a strategic one.