I host a number of low traffic Drupal (drupal.org) websites. Several for a non-profit, a few consulting shops, a book & poetry site. Low traffic, but a couple sites use lots of drupal modules, so performance and resource limits can sometimes be issues.
I've used hotdrupal.com as my hosting service for some years. They've really been excellent. First rate. I've only needed support a few times and they've always been prompt and professional. But the big thing, for me, is the accounts are highly optimized for drupal. My webpages load in less than 200 ms (thats a Drupal Devel module timing number). I've toyed with other hosts but nothing comes close. Part of it the large php memory_limit = 160M in the stock php.ini for my account. Nice. But they've obviously got other optimizations too.
Still, nothing lasts forever. As Drupal grows, and as my websites grow, I've used more and more resources. Currently I'm bumping into my account's 3GB disk space limit. And that includes the MySQL databases. One of those is using > 400 MB. That's as reported by Cpanel, which is the number that counts toward my allowed quotas. phpMyAdmin reports less than half that number, but I gather this discrepancy is fairly common.
Now, hotdrupal.com isn't all that generous on disk space. They say they provide premium disk space (meaning fast), so they can't provide unlimited amounts of space. I'd just get more diskspace, but for the incremental cost I could price myself into another provider.