I have seen some photos of non-Japanese people with tatoos and noticed a difference between Japanese ones and theirs. They usually have one or two small ones on the upper arms, or on the chest, or on the thighs just as a fashion as far as I have seen. (Well, I saw one of the forum members proudly saying her father has got 80 or more, so I might be wrong.)
On the other hand, Japanese yakuza, who are already criminals or at least would-be criminals, usually have large ones all over the back to the shoulders and upper arms and sometimes more like this photo I linked below.
http://pds.exblog.jp/pds/1/200605/31/64/b0036864_1591336.jpg
A guy who was in the same class as mine at junior high school has got one all over his back when he just joined a small branch of Yamaguchi-gumi at the age of 17 in Tsushima City, Aichi.
The following story is what he told me recently:
When they found him, a bad boy (a rogue?) who was a school dropout and without a job, (actually he was a member of bousouzoku then ) they blandished him into the yakuza branch and got him a large tatoo which was very expensive by lending him the money. He said he was very honored and proud of it back then and was always showing it off to his friends. Soon he got sick of the life there and escaped, then some of them came to his mother's house and thretened her to give him back to them or she must pay back the money they had lent him for the tatoo. So, seems like the large yakuza tatoo is not only used to scare people but also used to chain the members. (Well, if you had such a big tatoo all over your body, it would be very difficult to get back in to a normal social life even though you have already paid back the cost... )
However, in recent years, I see some young people (male and female) who are obviously non-yakuza have small ones just like non-Japanese has as a fashion. I suspect most of them are fake (stickers) but maybe some are real.
And .. to answer miki-chan's questions:
Yes, normal people frown upon the large traditional Yakuza tatoos but not on the small fashionable ones.ツ (Maybe elderly people still frown upon the small ones too.) And lots of public baths have signs saying "No Tatoo Allowed Here" or something like that, referring to the yakuza ones.
Oh, what has become of my classmate? Well, he ended up working at a Takoyaki Yatai without getting much paid, still at the bottom of the yakuza social pyramid.