Thirty million Americans can't be wrong. Or so Europe seems to think as it catches up on cable TV under a high-flying shadow that threatens to make cable broadcasting obsolete.
The shadow - or glow - belongs to the DBS (direct broadcast satellite). Its increasing power permits home consumers to receive video information and entertainment on smaller and smaller ''dish'' antennas without benefit of cable.
Yet American cities and households continue to get wired for cable TV. By now there are many more than the 30 million US cable TV subscribers estimated in May - some 35 percent of 83 million households having TV.
Certain European countries, especially the smaller ones, already have a much higher cable ''penetration,'' to use the industry's term. But the other English-speaking land, Britain, lags somewhere below 20 percent.
Now the push is on for more cable. Britain plans to wire all its big cities with 30-channel cable and have half of its households connected by 1990. West Germany has more than doubled its planned spending on cable TV this year on the way to a nationwide cable network. France intends to move ahead with emphasis on advanced optical-fiber wiring instead of the coaxial cable that has been customary elsewhere. The Netherlands is forging ahead with a large-scale experiment in two-way cable TV.
It is this two-way capacity - for home shopping, banking, and other communications - that remains an advantage of cable over direct broadcast satellites. Also, it currently offers scores more channel choices.
Such assets give cable a number of years more as a window of opportunity before the rise of DBS, according to US industry spokesmen. They see further competition in videocassettes, regular broadcast networks, and any other means of delivering the material that consumers want to see and hear. And they seek relief from some local practices and regulations that have applied only to franchised cable operators.
The Senate has passed legislation, welcomed earlier on this page, to foster order and fairness in the local marketplace. It contains a valuable provision to protect the privacy of cable subscribers, requiring their consent for the collection of any personally identifiable information and guaranteeing their access to any such information. Doubtless further protections of privacy will have to be considered, as the potential for misuse of massed information, even when not personally identifiable, is analyzed.
Will Europe - and the rest of the world that will eventually be hooked up by cable and DBS - look to the US experience on policy as well as technical and commercial matters?
Various American firms are entering into joint ventures with the Europeans. But the European nations are diverse in their policy approaches. There are different mixes of public and private participation, different views of whether to allow commercials, different copyright laws.
Democratic France and West Germany, for example, appear to be keeping a tight rein on how cable develops, while Soviet-dominated Finland ironically allows competition free play. While the West Europeans support the free flow of information - and oppose communist efforts to restrict broadcasts from one country to another - some of them are trying to shape cable so as to maintain some control on what is available to their populations.
There will be many technical questions as the various kinds of broadcasting burgeon - questions of frequency allocations and satellite placement like those on which some new world agreements have been reached in recent years. But the bottom line may be a new challenge to international tact and integrity, especially when the wires are cut or replaced and those direct broadcast satellites can beam almost anything to the ''dish'' in almost anybody's attic.
Then a country that can broadcast to another country what that country's government does not want will have to decide whether it should do so. Should the government be defied and the citizens be allowed to choose from the whole broadcasting marketplace? Matters of taste as well freedom are involved. Once more, a technology making virtually all things possible renews humanity's reliance on the moral and ethical principles that leave technology behind.