Hmmm... I'm under the impression that most people who say kanji is unnecessary or inefficient are those who are not fluent in Japanese. In fact, kanji creats great efficiency especially in reading.
Following is a part of an article from Asahi.com.
日中首脳会談は8日午後に
安倍首相は8日朝、政府専用機で中国・北京に出発し、 同日午後に歓迎式典で迎えられた後、胡錦涛(フー・チンタオ)国家主席との首脳会談を行う。前後に温家宝(ウェン・チアパオ)首相、 呉邦国(ウー・パンクオ)全国人民代表大会常務委員長(国会議長に 相当)とも会談し、夜には温首相主催の晩餐(ばんさん )会が予定される。
Since kanji has meaning, we can understand the content of the text at a glance. I forgot where I read it, so I cannot give the backing source (pity), but some test proved that average time required to get the same amount of information from English text and Japanese (mixture of kanji, kana) text, Japanese text takes far less time compared with English - because of kanji.
にっちゅうしゅのうかいだんは8かごごに
あべしゅしょうは8かあさ、せいふせんようきでちゅう ごく・ぺきんにしゅっぱつし、どうじつごごにかんげい しきてんでむかえられたあと、フー・チンタオこっかしゅせきとのしゅのうかいだんをおこ なう。ぜんごにウェン・チアパオしゅしょう、ウー・パンクオぜんじんみんだいひょうたいかいじょうむい いんちょう(こっかいぎちょうにそうとう)ともかいだ んし、よるにはウーしゅしょうしゅさいのばんさんかいがよていされる。
Without kanji, it is difficult to see where a word/phrase starts and ends, also it takes ages to understand the text correctly - かいだん? Is it steps, ghost story or conference? せい ふせん ようき? Holy post-it vessel? Oh no, it's せいふ せんよう き - chartered government jet! こっかいぎちょう に そうとう? National Assembly Chairman and President? No, it means "equivalent of National Assembly Chairman".... Telegraph used to be printed in katakana only, and that caused many mistakes and problems.*
(Besides, hiragana takes up a lot more space than kanji - another advantage, efficiency of kanji is a few syllables can be covered just by one kanji.)
Kanji makes it easy to understand.
Personally I find the opinion that the complicated writing system of Japanese language is used to prevent foreigners to integrate, or make it hard to access for them, etc. really absurd.
Japanese language is first and foremost the communication tool for Japanese speakers. We use it daily, we need to convey our thoughts and ideas, everything, correctly and efficiently. We have no reason to make it too complicated or difficult.
It is not something we created to keep ourselves to ourselves and not to let foreigners understand us! If kanji were a factor to make our daily communication too compliated or difficult, would we bother to use them and make our life difficult, just for the people who do not have to speak it and use it daily? No!
Japanese written in romaji is even worse.
Before Japanese word processor and internet were introduced, international communication was quite limited. I was at the very end of the generation that used telex (and no longer with paper tapes, there already was monitors with keyboard to send out messages). Fax was still expensive, so daily communication was made by telex. You can use only alphabets and limited number of marks, and it was really difficult to communicate Japanese people overseas - writing is not too bad, but reading Japanese in romaji is - like hell.
*off-topic note:
Funny (and maybe famous) example
(1)
Telegraph sent by a son to his father:
カネオクレタノム
The father replied
ダレニモラッタ、アマリノムナ
(Who gave it to you? Don't drink too much)
Actually the son meant カネ オクレ タノム (Send money, please) but the father misunderstood it for カネオクレタ ノム (got money, I'll drink).
(2)
A journalist from a newspaper visited another journalist from another paper for an interview. When leaving, the journalist asked to send a telegraph on his behalf, to tell them he's going back.
キシャノキシャハキシャデキシャ
which sounds very confusing, and actually means
貴社の記者は汽車で帰社
The journalist of your company is going back to the office by train.