At one time Softbank owned about 30% of Alibaba worth about $200 billion, making Softbank chairman Masayoshi Son, very briefly in 2000, the richest man in the world.
The Alibaba stake, which had been acquired for $20 million, helped underpin the extensive borrowings of Softbank which currently amount to around $170 billion.
Son is reported to be personally liable for about $5 billion under compensation deals done with Softbank.
The situation makes the fate of the Arm IPO later this year particularly critical for Softbank.
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