IMHO, customizing is as good or bad as (spare the analogy) dress-code in a work place.
When it exists, people will be looked at in the same way, as equals, we're comparing apples with apples. What we wear is out of the equation and the only thing behind it is only our personality traits, it makes us focus on what's important and not be distracted with other stuff.
When it doesn't exist, the baseline for comparison gets gray, you start comparing apples, oranges, apricots, pineapples (er, I think you know what I'm saying). In this regard, people will start noticing if you wear shorts and sandals vs pants and shoes, instead of noticing what you have to say.
Giving people to customize will make the baseline for comparison gray, will make users stressed about not finding they need where they expect it to be; it assumes (badly) that everyone has the same good communication skills and that everyone will be perfectionist about the way their profile looks, and well this is not possible.
A workaround that would allow users to customize without you compromising experience is doing something like the cover photo in facebook. Facebook has been (debatable) clever about this, and introduced this feature gradually. It made users request it before they would automatically switch, this way, if someone wanted to customize his/her profile, the first step was to request it, and the second step (inherent) to the process, was to customize it. All of the profiles that used the cover photo at the beginning would be customized. Now it's very difficult to find profiles without a cover photo (but they still exist and look ulgy). Customization is small, it is uniform, allows users find what they want in the expected places, but gives a huge sense of embedded personality to the page.