> SpaceX basically has just one customer which it is entirely reliant upon.

As far as I can tell NASA accounts for less than half of SpaceX's business. According to their website they have nearly $5 billion in contracts and I can only find reference to just over $2 billion in NASA contracts.

> As far as I can tell NASA accounts for less than half of SpaceX's business.

NASA ⊂ "The Government"

SpaceX also has Defense (USAF) contracts. At least around $900 million already awarded (and that may not be all), and they recently sued to be allowed to compete for much more under the EELV program.

Good point, I hadn't realized the USAF contract was awarded to them yet. That puts government funding at significantly more than half of SpaceX's existing contracts. I still wouldn't say they basically have only one customer, but it's closer than I thought.

With the "technological moat" SpaceX is building, does it matter how few customers they have today if no one can compete with them?

Didn't a SpaceX competitor install second-hand 1960s Russian rocket engines in a launch vehicle that failed recently? Its not a fault on the engines - I'm sure they were excellent - but rather an anecdote on the gargantuan barrier to competition inventing new space technology offers SpaceX.