Bandlimiting and OFDM spectrum - what is considered "bandlimited"? I have been reading about OFDM modulation, it's not clear to me how you can have band-limited OFDM but given its prevalence in wireless communication there must be some designation of approximately band-limited that OFDM satisfies.

So my question is how is the bandwidth of OFDM systems calculated and if it's an approximation based upon the largest spectrum lobe, why is that good enough?  

It doesn't even look like OFDM systems are pulse shaped to reduce the side-lobe strengths so what's going on?
This isn't a question specific to OFDM:

All transmissions need to be bandlimited by law. Hence, law defines band-limited here.

Typically, this happens in the shape of spectrum masks (often expressed in textual form in regulations); these say something like (this is just an example, actual legislation varies across regions and is definitely different):

"not more than -40 dBm/Hz within 10 MHz of the carrier frequency, not more than -90 dBm/Hz between 10 and 20 MHz of the carrier frequency, and -120 dBm/Hz more than 20 MHz away"

Regarding the specialties of OFDM:

You indeed can't pulse shape OFDM without losing its benefits. (You can do a bit of a tradeoff, and trade a bit of orthogonality for out-of-band radiation suppression, but you'd typically avoid that)

That's why you typically have "empty" carriers at the edges. You simply leave room for the sinc to decrease.