To me this is quite simple. Recent college graduates and/or those with less than two years of experience should be on one page. However, if you have years of experience it should be on two pages. If too many years of experience are crammed on one page it is not only visually unappealing but important information may be left out. The bottom line is that most managers will read your resume once you have gotten their attention even if it is more than one page.
The exception to the rule is if someone has been at the same company for 10 years or more as they can show a nice line of progression (if they have had more than one title), their responsibilities, and accomplishments in one quick snapshot which is very appealing and informative.
Let me know what you think. Go to www.resumerd.com and comment on Ask Resume Road! Have a wonderful day!