Did you know that US anti-trust laws are designed to protect consumers and not competitors? And did you know that not every one looks at it this way?
Here is a good article on the subject.
Irish Times Article on Google Judgement by EU
And that led me to this article, which is older but gives some more context:
Wired Anti-Trust Article
This is why Amazon doesn't get prosecuted for monopolistic practices, but Apple did for price-fixing on books. Amazon lowers prices (good for consumers, bad for competitors) and Apple was trying to raise them (bad for consumers).
The European Union would look at this differently. They say that one company possessing too much market-share is inherently bad for the marketplace.
Can you really trust an Amazon to keep having a focus on low prices? What about when there is no more competition?
To answer that question I found one more article. You have to dig, but it's there at the bottom of the top paragraph of page 4:
Comparison of USA and Europe Anti-Trust Policies - PDF
Basically, you can trust them if their anti-competitive (but pro-consumer) price lowering has to stay low because any raising of prices will result in new players immediately entering the market.
What does all this have to do with technology? Well it helps explain some differences between the US and Europe.
The other thing that is related is that there isn't really a software or online business that isn't susceptible to a new competitor.
To create software you may need software developers and servers, but you don't need other raw materials or a factory, so the cost is much lower than in analog industries.
Software business are inherently winner take all because world-wide delivery is so simple, there are no geographic restrictions on products, therefore the best will win and when they win they will win very big.
But they can only stay on top if the innovate relentlessly or buy companies who do.
Otherwise someone will find away to come along and eat their lunch.