Obviously Mossack Fonseca are yet to be accused of any actual illegality as a result of this leak and they and their staff should of course be presumed innocent until any evidence is produced proving the opposite. However, speaking in very general terms, Chinese interest in Panama over the past decade or so has centred around two things: the canal that facilitates much of China's trade, and what is known as the "Panama Route" for moving money out of Mainland China, especially where the money has been earned in a way that might not be entirely legal.
Chinese interest in building a new canal across the Cantral American isthmus appears to have flagged somewhat, especially as the expansion of the Panama canal, which was well in hand when I visited that country, appears to render any new canal entirely redundant. The "Panama Route" on the other hand, is quite different: supposedly it works by smuggling money out of Mainland China to another country (South Korea is the one I've heard about, but others may work as well) and then wiring it from there to Panama. Once the money is safely in Panama, so legend has it, since Panama does not have diplomatic relations with the PRC
but instead recognises the Republic of China, it is almost impossible for Mainland Chinese authorities to touch it.
Interestingly, the Panamanian government even sought to switch recognition to the PRC as recently as 2009, only to be rebuffed by the PRC government out of
an apparent desire not to breach the diplomatic truce between the two sides of the Taiwan strait. Funnily enough, despite the end of the "truce" with the recent establishment of diplomatic relations
between the Gambia and the PRC after their 2013 breach with Taipei, there has not been any sign, yet, of movement in the Panamanian case despite the long-expressed desire to switch recognition.
The suspiciously-minded might suspect that the PRC leadership are purposefully delaying the switch as the "Panama Route" is rumoured to have proved useful for them and their families. However, there is not nearly enough evidence at the moment to draw this conclusion - but if Panama's diplomatic switch from Taipei to Beijing is significantly delayed, you might be forgiven for thinking that their motive in doing so may have something to do with keeping the "Panama Route" open.
[Picture: a view through the fortress wall at San Lorenzo, Panama, which I visited with my wife whilst on honeymoon last year]