For that matter, you can also set a default text-scaling level as well (mine is at 130%), which I tend to do in addition to force enable zoom. Many sites have fonts that are too small on a phone imho... they really should be at least 12pt for most text assuming that proper scaling meta is set... Too many sites use 9-10pt fonts which are just really hard to read.

I'm far sighted, so my phone is literally the hardest thing for me to use much of the time. One of the worst offenders was the Facebook app, which didn't seem to even follow Android's setting for using larger fonts. I've since stopped using the FB app (way too much battery usage), and just use the mobile site, which isn't much better in terms of usability.