Question: I have this observation of mine, that good (usable) user interfaces on the web are usually at their best upon the launch of the web site and some time after that, and then, as soon as the business behind the web site becomes successful (if it does become such on the first place), the great UI gets gradually ruined over the course of the success of the business (especially if that is an online business amassing a sufficient number of users to make it either a monopolistic or oligopolistic player). Do you have any observations confirming or refuting mine?

Answer: 
Disagree. I think Amazon, for example, has done a pretty good job in terms of improving the information architecture (IA), search and personalization of their interface over the years. I suppose this is the kind of "monopolistic" company you're referring to? It is true that IA often gets more bloated as companies add more elements to their nav over time. But this can be kept under control with careful organization and user research techniques such as card sorting.
### Classic Small Business vs. Big Business Attitude

I have had a theory for many years about this. It is **NOT** specific to "Web Interface." In fact, the typical small business will have a minimal web presence and therefore may not have much of a "Web Interface" to speak of at all. Now my theory:

All businesses starts small. Most either stay small or fail. A very small percentage become big businesses. For an example, compare how many small grocery stores, pharmacies, etc. there are (though admittedly not as many as there used to be as many have been swallowed up by bigger companies or closed due to competition from bigger businesses) compared to large grocery store chains or pharamacy chains, each of which can include hundreds, even thousands of stores. So there is actually a relatively small group of big businesses to compare.

In my personal experience (yes, opinion based), there are companies within each industry that have managed to take the "ideal" small business attitudes regarding customer service (personalized, "customer is (almost) always right", easy returns), employee treatment (not so much salaries as benefits, flexible time off, high morale), community involvement (e.g., supporting charities) and other factors. **A high-quality web interface is simply the latest of those "customer oriented" factors.**

There are other companies that have managed to grow large, either based on those same attributes but "losing" them along the way at some level, or purely on price competition (where, depending on the market and other factors, people will buy **despite** poor customer service), government sanctioned near-monopoly (whether by government regulations, shaky patents or other methods) or other methods to become **REALLY BIG** without those cherished small business attitudes. At a certain level, a business can become "too big to fail" and survive for a relatively long time despite these problems, including (in the modern era) a web interface that is far below expectations. (Though for anyone who thinks a business is truly "too big to fail" can simply look at the downfall of Sears after over 100 years as a leader in US retail.)

In fact, I have actually seen some big businesses with fairly decent web interface, but unable to compete successfully against other online retailers due to other factors, and with all of the other problems mentioned above conspiring against them, in the long-term, in the bricks & mortar world.

While I won't list my personal opinions as far as which big companies fall into each of these categories, as that is arbitrary and subjective (except of course that *my* answers are the right ones!), I think most people who do a lot of shopping at multiple large stores of a particular type (department stores, home improvement, grocery, computers/electronics, pharmacy), can come up with a categorization of which ones have a "small business attitude" based on multiple factors, including web interface.

The end result is that "quality web interface" is only one of many factors and does **NOT** necessarily change (for better or for worse) with the growth of a business.