At 106 Miles we see a lot of entrepreneurs who aspire to build the next billion dollar company.

What's interesting about 2011 is that there's a growing number of people who have done it.

TechCrunch's talk of the billion dollar valuation club reminds us that most of them are so-valued because their revenues are growing at a tremendous pace: Airbnb, Square, Spotify, Dropbox, Gilt Groupe, and Foursquare.

Their business models respectively are: marketplace, transactions, commerce, paid storage, deals, and advertising/deals.

They join startup heroes of the last decade Pandora ($2b), Living Social ($3b), LinkedIn ($6b), Twitter ($10b), Zynga ($10b), Groupon ($25b), and Facebook ($50b).

Their business models respectively are: advertising, deals, subscriptions, advertising, virtual goods, deals, and advertising.

There are many ways to get to a billion dollar valuation -- we in the Internet industry are inspired by Google, Yahoo, eBay, and Amazon -- but it's helpful to remember that every single one of them started with nothing but a great idea and a can't-die attitude.

I want to emphasize this point to 106 Miles members: from the above list of winners, it would appear that starting a company is easy.

It is not easy to start a company. Let me repeat that: Starting a company is hard.

Even the companies listed above went through many ups and downs. Five examples:

1) LinkedIn only had two interested investors at the beginning.

2) Pandora pitched 348 investors before it found someone who wanted to invest.

3) Airbnb had to sell cereal to stay alive. They lived off the cereal and refused to die.

4) Foursquare is two years of success after ten years of failure says founder Dennis Crowley.

5) Twitter started as a project inside Odeo, which eventually had to fire everyone and shut down.

I'm sure if you looked at every one of the "billion dollar companies", every single one went through many trials and tribulations.

So remember, it is hard to start a company. There are many ups and downs, even for the companies that make it big.