At least this problem is now acknowledged in Japan.

It has been acknowledged in various forms such as news report and documentary etc.

Years ago, I had a Japanese colleague ・・・

I am afraid your colleague does not represent Japan.

In a postwar mess, homeless was a fact of life. They were called furousya, homeless children were called furouji. Tomorrow’s Joe(en.wikipedia.org/wiki/Tomorrow’s_Joe) was one of them. You used to see homeless lying under a railroad overpass. At the time cities developed, they were evicted. There were battles between homeless people and administrators who tried to evict them. There were a lot of news reports on that. After the bubble economy, journalists started paying attention to new type of homeless;people with bachelor’s degree and presidents of the company became homeless. Years ago, “ホームレス中学生” a homeless junior high-school student” became a best seller.

News reports on homeless are aired regularly especially when society is hit hard by recession;lives of homeless, how they became homeless etc.
And homeless is a popular topic for documentary

路上に賭けた人生　～ビッグイシューという挑戦～
http://www.fujitv.co.jp/b_hp/fnsaward/14th/05-246.html
THE ホームレス ～野宿労働者1万8千人の実態～
movie.goo.ne.jp/dvd/detail/D112307857.html
俺達だって何かを創造できるはず
http://www.youtube.com/watch?v=Mh6uROZT8dI
歌舞伎町のこころちゃん 4才のホームレス少女2
http://www.youtube.com/watch?v=O__Jaqu-IIM
NNNドキュメント「派遣切り ネットカフェ難民5」
veohdownload.blog37.fc2.com/blog-entry-1673.html
You can find a lot more.
(I was looking for a masterpiece documentary which depicted the love between old homeless man and woman at Asakusabashi, but I couldn’t find it.)

By and large, many people see homeless people as just people to be avoided while some people try hard to tackle the problem.

We have, on any given day, anywhere from 750,000 to a million on the streets here in the US.

It’s also estimated that anywhere up to 3.5 Million are homeless throughout the year these days, in the United States.

２.調査客体
　 法第２条に規定する「都市公園、河川、道路、駅舎その他の施設を故なく起居の場所として日常生活を営んでいる者」

３.調査方法
・全市区町村における巡回による目視調査
http://www.mhlw.go.jp/houdou/2008/04/h0404-1.html

ホームレス
http://ja.wikipedia.org/wiki/ホームレス

定住型と移動型 [編集]
ホームレスは、定住型と移動型に分類される。
定住型は、公園・駅舎などの公共の場を一定期間占拠し、段ボールハウスなどを設置して生活している。しばしば公共の場の不法占拠かどうかを巡り行政と対立する

Anyway the figure will go higher, I am afraid.