Ok, just to clarify some sizes of cities and populations. This info is all taken from the US Census Bureau Quick Facts pages. Some of the population numbers differ slighlty from the US Census Bereau's American Fact Finder page but I am just using the quick facts page. Listed in order of size (square miles)
City_______________Population(2006 est)____Sq Miles_____Pop per sm
Phoenix____________1,512,986_____________474_________2,782.0
San Antonio________1,296,682_____________407_________2,808.5
Albuquerque________504,949______________180__________2,483.4
Denver____________566,974_______________153_________3,616.8
Portland___________537,081_______________134_________3,939.3
Salt Lake City______178,858_______________109_________
1,666.1
Seattle____________582,454_______________83__________6,717.2
Boise_____________198,638________________63__________2,912.9
Ok I don't like those numbers. The one that sticks out the most is the population per square mile. Obvioulsy that is an issue considering the city limits go well into the mountains, where many of the other cities on the list don't have those issues.
On the above list SLC is the smallest population wise, even behind Boise

, if SLC had just the average population per sm that the others have 3,608.4 it would increase the population to 393,320
It will be interesting to see what the 2010 census says about the population and if it has increased as expected.
Ok I wasn't really for it, and despite the fact that the townships don't want to be incorporated maybe it does need to be done. I would say Magna, Millcreek and S. SL. S SL is listed as 22,038, E. Millcreek at 21,385, Millcreek at 30,377 and Magna at 22,770 (2000 census). That would place the SLC population at 275,428. While not huge much better.
Here is a list of the same areas by MSA. Population estimates as of July 1, 2007
Phoenix-Mesa-Scottsdale_______4,179,427
Seattle-Tacoma-Bellevue_______3,309,347
Denver-Aurora________________2,464,866
Portland-Vancover-Beaverton____2,175,113
San Antonio__________________1,990,675
Salt Lake City_________________1,099,973
Albuquerque__________________835,120
Boise-Nampa__________________587,689
Retailers base location decisions off of MSA and surronding MSA data, NO national retailer will base a location decision on only city population. Business owners may not however, but relocation firms do rely on MSA data. So fact based decision making won't change dramatically, but impression based opinions can change. That is when, as i have mentioned before, many business executives will go off personal likes and dislikes.
While it would be nice if SLC had a larger population, but along with a larger population come larger issues and sometimes larger problems. We all love SLC because it is a great city and has grown at a steady pace and managed that growth. If we want SLC to continue to love SLC for whatever it is each of us loves about it, the growth needs to continue to be steady in my opinion. SLC and the MSA are in a place that many other MSA's would like to be in, a much stronger and more resilant economy than a large majority of the nation, a growing population. Midwest industrial based economies would love to have any sort of population gain. SLC proper is expected to add over 10,000 residents just to the CBD, between 2005 and 2010, with an overall gain in the total city population expected also. Midwestern MSA have a stagnant population for nearly 4 decades and the core cites are hemoraging population every year.