A few minutes ago the site unceremoniously let me know the limit on the number of keywords in an Ad Group: 2,000.
You would have a better CTR if you can divide them into smaller groups and write a more focused title/description and set up multiple adgroups. Just my 0.02!
For the time-deprived webmaster, sometimes it's better to get a 1.0% click-through rate on hundreds of terms, rather than no click-throughs because you didn't have time right then to shoot for a 3.0% rate by splitting everything out.
When I get around to it, I split them up.
Also, I don't know if this happens to others, but AdWords screens crap out on me a lot. No amount of bandwidth on their end seems to be enough to handle demand. So I get in and get out.
Additionally, when we lose a term, say "get widgets", due to low click-through, sometimes a temporary measure until I have time to investigate is to submit it again, with a load of third words like
get widgets a
get widgets an
get widgets 1
get widgets 2
get widgets the
get widgets for
get widgets to
There's no sense in creating separate groups for that. It's the same term.