It would really be great if the next hardware revision of Photon had pull-up resistors for D0/D1 for I2C operation. Maybe add 4 solder pads to the bottom of the board to enable this feature. Yes, I understand it would add cost to the hardware.
Some of the hardware I use “Sparkfun” have pull-ups but most don’t.
I also understand on some other platforms, the pinMode “soft” pull-up feature can be enabled eliminating the need for resistors. I don’t know if the Photon’s internal pull-up resistors are in the 4.7 - 10 K range however.
Just a thought for the next gen!