Difficult, isn't it. In the recent examples, you have Renshaw, who is as Yorkshire as they come but has grown up in Australia from the age of ten (though from what I hear does not hold an Australian passport), and Jennings, who has played age group cricket for South Africa but who has a British mother and strong roots here. Neither is massively offensive - they both have close ties to the country they have chosen to represent, so its hard to judge them adversely.
By comparison, some in the past, like KP, Symonds and Trott, who were going back through the generations to qualify, look more cynical.
As a whole, I think cricket has things more or less right - certainly compared to Rugby Union, where most national sides take their colours less as a badge of allegiance and more as a loose starting point for negotiations. In recent years, Ireland and Scotland have openly recruited from Super Rugby to fill their problem positions on a three year residency farce, whilst Australia and the great All Blacks use the same opportunities to fill out their sides with numerous pacific islanders.
The recent Australian tourists had 13 (if you include injury call ups):
Tonga - Latu, Timani
Fiji - Naivalu, Kerevi, Naiyaravoro, Speight, Kuridrani
South Africa - Haylett-Petty
Zimbabwe - Pocock
New Zealand - Houston, Cooper, Faulkner, Lealifano