I've been working as a full-time salaried (insert whatever term you like here for people who write code) for coming up on 13 years now.
This past month, going through the process with a potential new employer, was the first time anyone insisted on contact information for my previous jobs and made any effort to try to check on them. I have worked at both small (startup) and large (household-name) companies, at increasing levels of seniority. None of them ever did that.
When working menial jobs, that required little skill, and no prior experience, references were almost always asked for, and sometimes checked.
As a software dev, moving across multiple large companies (large defense contractor, international broadcast network, international multi-industrial, well known video streaming site), from dev, dev II, senior dev, lead, manager, I've never had anyone even ask for references (I've seen one or two application systems that requested them when I was job hunting; I just didn't apply to those jobs).
> Tell me a little about Jim's day-to-day
> Sure... Jim is an above average junior software dev...
> Sorry you say junior or senior dev? Does Jim have team management roles?
You can give a glowing review, but depending how how Jim portrayed himself, the review can be taken by the recruiter as a net neg/pos. To directly address your question - I don't think there's much down-side for a reference to always provide a positives reviews. Just keep in mind that an experience recruiter will probably realize this too (they've probably been burned before), and have some clever ways to ferret out the key info they're after.
I think the "references" under discussion here are actually phoning up former colleagues/managers for more detailed questions.