I use thousands upon thousands of keywords, split across about 250 ad groups. Each of DaniWeb's 100 forums has about 2-3 ad groups. For example:
Forum being targeted: Networking
Ad Group: Networking - Routers
Keywords: router, routers, routing, using routers, about routers, with routers, configuring router, linksys router, cisco router, etc
Ad Group: Networking - Switches
Keywords: switch, switches, switching, using switches, about switches, with switches, configuring switches, linksys switch, cisco switch, etc
I'm not saying I actually use those exact keywords. That's just the general idea of what I do.
I think this really depends on the size of the company and the budget. If you want tons of traffic than you target lots of keywords. If you are a niche company that target only highly targeted keywords that will convert.
In my opinion, Its not having any problem with your word count, Depends upon how much keywords you can target for your campaign. The main thing you need to bother for is relevancy of your keywords related to your business. More over that You can try for making keyword phrases that may help your keyword counts less and optimizing for more keywords by this way.