I'm generally pretty confident when creating bibliographic records for DSL's catalog - when cataloging for your own institution, you can bend or even break just about any rule you want, as long as you understand the implications of what you are doing (VERY important, since many of the rules were created for good reasons) and make sure you do it consistently. I'm a little less confident about adding records to the WorldCat database - I try to make sure that my records follow national standards, but sometimes the standards aren't always clear. However, if I code my records in the right way, others can edit them (the records in WorldCat, not the records in DSL's catalog) without too much trouble if necessary.
For me, the biggest problems arise when I come across a record in the WorldCat database that I know matches what I have, but the record is really awful. Any record with ELvl code 3 (doesn't meet Minimal-level cataloging specifications) or 8 (pre-publication level, such as records based only on CIP data) would be a good example. I know that I should and could edit and improve these records, but I'm not confident about doing so. A couple months or so ago in AUTOCAT, people were wondering why they so often see ELvl 3 records that haven't been upgraded and yet have lots of holdings attached to them. Many people posted, explaining that they (like me) do all or most of their cataloging in their local system - it would take additional time and effort for these people to upgrade these records. If I could go back to that discussion, I would add that not everyone has had the training to know what could/should be upgraded or replaced. OCLC has a chart that is helpful under certain circumstances, but formal training in what to do and when (or, alternatively, someone checking records upgraded and replaced by "newbies" and letting them know when mistakes have been made) would be nice.
Now that OCLC is starting its Expert Community Experiment, I think I might look into resources and training opportunities that would help me feel more confident about upgrading and replacing bibliographic records in OCLC. I'm currently signed up for one of the Expert Community Experiment information sessions, although I doubt I'll be a big contributor to the experiment.