A friend asked me for advice on giving coworkers plus ones or not after reading the "Date Dilemma" post from last month. I've read some conflicting advice on this topic. If you look on the knot.com you can find lots of helpful guest list Q&A, so I would encourage you to look it over. I think my best advice is to assess your specific group of invited coworkers. Personally I would make this decision by asking myself a few questions...
1. How crammed is my guest list already?
2. Do I (or my spouse-to-be) know my coworkers spouses, sig. others, partners etc. well?
3. Are the majority of invited coworkers married?
4. Married or not, could my work crew all attend as a group of singles and still have fun?
5. Are there other singles being invited who they could mingle with?
If my guest list is kinda tight...I would seriously assess if the work crew could all attend as singles and have a good time together and/or with other singles. Even though some may have spouses, I likely don't know them, so I think saying to your work friends, "Yes I would love for you to be a part of my special day, but due to my big family, I'm inviting people from the office to come stag," is totally acceptable. Chances are all your work friends will love to hang out as a group.
If my guest list is not super tight... I would still have the above thought (no reason to spend extra cash). However if 9 out of the 10 co workers you're inviting are married I would probably just invite all the Couples and give that one person a plus one. Seems fair.
Anytime with the singles, just decide what's best for your event, your guest list and YOUR HEART and stick with it. I think more than anything guests notice consistency when it comes to who got invited with or without dates.