For spoken language, Mandarin is the standard, the official one. The rest of spoken languages such as Cantonese, Hokkien etc are dialects depending on your province in China and community.
If it is the first time you are learning about Chinese languages, learn Mandarin and Simplified/Tradition written language.
You may wish to offer both Simplified and Traditional Chinese, but that's a choice — and the article is clearing up the confusion that most non-Chinese have about which relates to which nations.
Hong Kong, Taiwan, and the Mainland all write in Standard Written Chinese. Hong Kongers do not expect to see Cantonese in materials translated from a foreign original, and largely do not want to. HK/TW/CN have a few vocabulary differences (e.g. "taxi" is HK's "dishi", TW's "jichengche", and CN's "chuzuche"). Orthogonal to the vocabulary differences, HK and TW use Traditional characters, SG and ZH use Simplified. But I can write "chuzuche" in Traditional, or "jichengche" in Simplified. They still mean the same thing and are still understandable to all.
While we hope to offer translations into Traditional Chinese by Cantonese speakers in the future, currently our translations are not ideal if you hope to sell your product in Hong Kong.
Traditional to Simplified mapping is perfectly surjective. That is to say, it can be done by computer with 100% accuracy. Having a Traditional Chinese and a Simplified Chinese version of a document does NOT require two separate translations from the source document, as you seem to be implying.
Let me draw an analogy, Britain says "boot" and "bonnet" and "bobby" where America says "trunk" and "hood" and "cop". That does not mean everyone needs to get separate British English and American English translations, nor separate Taiwan Chinese and Singapore Chinese translations. In one extreme, if I were a high volume group-buying website looking to expand globally, yes of course I want the whole interface and the terms and conditions done up separately for each English and for each Chinese. In the other extreme, if I ran a boutique hotel and just wanted to give my Chinese customers directions from the airport to my doorstep, I have no need for separate translations.
In between is a giant grey area where full-service Language Service Providers generally try to provide some guidance to their clients. As a low-cost LSP maybe you are not aiming at the kind of client who needs this kind of guidance --- in which case you shouldn't be purporting to offer it. You should define yourself clearly.
The fact is that people in Hong Kong and Taiwan have a much higher literacy rate than those in mainland China, yet they use Traditional Chinese. Mainlanders' low literacy rate is mainly a sign of lacking education, not Traditional Chinese being a barrier to literacy. Moreover, in a digital world, they make no difference in input speed.
What Hong-Kongers and Taiwanese are opposing to is not the communist simplifying Chinese Characters, but simplifying them in an ugly fashion. In most cases, it breaks the consistency in word formation as seen in Traditional Chinese. In other cases, it's not aesthetic and even absurd. There is a joke saying that the word factory(廠)in simplified Chinese (厂) explains why factories in mainland China are subject to collapse.
Speaking of economics, simplified Chinese indeed appeals to larger potential customers. However, PRC put lots of restrictions on foreign corporations. That's why even Google and Facebook failed to (and will continue to) dominate in China. On the other side, Hong Kong and Taiwan have the goodies of free markets.
On the other hand, traditional Chinese on a <4 inch screen always PITA to read because every fucking single character looks like a black block, for example 龍, it's very hard to see the exact strokes which cause an obstacle for reading. (yeah, like 赢羸蠃嬴 are totally 4 different characters.) Traditional Chinese under 12px is simply un-readable on LCD screens.
The retina display on iPhone4 is good news for traditional Chinese.
On Twitter, 140 Characters mean a lot in Chinese! why? In Chinese, almost every character is a word; In English, every character is just an alphabet, not a word, with minor exceptions of course. Chinese words are square blocks whereas English ones rectangle blocks. They shouldn't be of the same height.
I would argue that Chinese words convey more meaning per cm square. The same square space occupied by 5 rectangle capital alphabets is more than enough to display any Chinese character correctly.
BTW, you don't need to recognize every stroke to be able to identify a Chinese word. You can tell by its pictorial pattern, such as negative spaces.
And somehow they missed a far better target of Zhuyin Fuhao.
http://en.wikipedia.org/wiki/Bopomofo
It would have not only vastly simplified the written language problem in China, but forced the nation to standardize on Mandarin as the spoken tongue (with the benefit of a standard pronunciation!)
Most of the homophones are sorted out with the tonal marks anyways, and in cases where that doesn't clarify enough, there's usually less than 9 homophones anyways making a single numeric subscript a reasonable clarifier.
(written in traditional): 繁體字 (written in simplified): 繁体字
Also, the bit about traditional characters being harder to learn reads like propaganda. Traditional character-using areas have higher literacy rates. Also, my own personal experience as a language learner has been that traditional takes longer to write, but it's more systematic in its structure and it's much easier to read.
One further thing worth pointing out is that mainlanders read traditional characters far better than Taiwanese and overseas Chinese read simplified.
Song(CN)/Ming(TW)/Mincho(JP) ≍ Serif
Hei(CN)/Gothic(JP) ≍ Sans
Kai ≍ Script
There was (or still is, politically motivated, I think) opposition to the simplification in Taiwan, but fortunately pragmaticism prevails and nowadays, even the current President Ma Ying-jeou advocates "识繁写简" (recognize complex, write simplified), because the practicality of the simplified version is undeniable.