I generally buy everything over the interwebz.
I've worked in shops for twenty years and over time I've learned how to do everything and have all the tools needed to build a bike from the frame up and the knowledge/experience to do so as well.

I live in a very small population area and there are not many riders. So saying the local shop is small, carries one brand of bike and very few parts. I stop in to chit chat and will buy lubes, etc.
Even their tubes are twice what I pay online...dirty secret time...shops make their biggest profit margin selling tubes...they cost little more than a buck each for a shop, imagine what the bit inteweb guys pay...and charge quite a bit.

I have more choices online and the prices are always better.
Generally I only buy tires, tubes, etc. online as I have enough parts squirreled away to last the rest of my life...when I moved from the Boston area I stocked up on parts I'd need at the bike shop I was working at...cassettes, brake pads, cables/housing, etc. to last a lifetime or two and all at very good shop cost prices.