Remember that one of the goals of StackExchange is to "teach people how to fish" instead of just giving them the fish. Aside from the logistics of the list (see next section), asking for a "Who" or "What" answer often means that you're just going to get a fish. Asking "How" and sometimes "Why" will give you the fishing lessons.
The other issue with answering the "Who" or "What" is that you're making a list. Lists don't sound bad at first, but there are some gotchas that can arise, and your question specifically is particularly vulnerable to these issues. For example,
- Conflicts of interest: I could be recommending my own design firm without fully disclosing that I have a stake in that firm.
- Stale lists: Not only do firms come and go, but their reputation can change quickly. For example, see Bernie Madoff.
- Quality of answers: There is no guarantee that each recommendation has been fully researched and vetted.
So to be a bit more explicit, here's some examples of what I think would be OFF topic:
- Please recommend a design firm for a project that I am working on
- Please recommend trusted sources and listings of providers of EE and programming services
However, I believe that the following would be ON topic:
- How can I find reputable electronics design firms?
- How can I vet an electronics design firm if I am not experienced in electronics?
- How can I prepare my project for a design firm to get an accurate quote?
A design company may be recommended as a result of these discussions, but you would be able to understand why the firm was recommended instead of just knowing that "some guy on the internet recommended this firm".
