All of the big booster manufacturers have had their share of failures, often very expensive ones that were traced to mundane causes (e.g. a software failure on the Ariane V's first flight as but one example). Boeing, despite decades of experience, had two out of three of their Delta 3 boosters fail. This was in 1998 and 1999. They've had much better results with their Delta 4 but the first flight of the Delta 4 Heavy was less than fully successful. Lockheed dropped a bunch of Titans over the years and Atlas boosters, while currently enjoying a good run of success, had a high failure rate for a long time. NASA (Shuttle), ESA and the Japanese, Russians, Chinese, Indians, and everyone else who has tried to build their own boosters have tasted failure. SpaceX may be no different.

Developing a new booster is a huge challenge. Developing a whole family of new booster (Falcon I, Falcon V, and Falcon 9) is even more challenging, especially when you factor in their designing and building their own engines. SpaceX has to not only prove they can build successful boosters, they have to do it cheaper than companies like Boeing, Lockheed-Martin, and Ariane that got huge government subsidizies to build theirs.

While I really hope their first Falcon I flight is successful, I'll try not to be too discouraged if it fails. This stuff has proven to be harder than it looks, both from a technical and financial perspective.