So, your connector blocks are likely at least 10pF per end, with some inductance too…
The resistor is there to help with the impedance mismatch between the low impedance output, the transmission line, and the high impedance receiver. It’s all black magic (and there are books with that title on this very subject) but here are some links which show how traces look on a scope and how much nicer they look with series termination by the source.
http://www.ctscorp.com/components/appnotes/AN1025_ClockTerminationDesignGuidelines.pdf
I can’t see any bypass capacitors (between GND and 3.3v) on your breakout. Are there any? This is essential as the inductance of the wires between the imp and the breakout will mean the high frequency current pulses taken by the chip (and the I/O) will play havoc with the voltage.
(it looks like it has a sparkfun logo on it, but it doesn’t look like any of the ADXL breakout boards they have listed on their website)