My file was 2GB in version 2006 and was limited by the Windows 2GB file size limit. That file cound not be imported into FTM 2008 due to out of memory issues with FTM.
Split files between my family and my wife's and files have grown to 65,000+ persons; 1,900,000 records; 49,600 images (mostly census, military records, Newspapers, DAR/SAR records) between the two files. Over 70GB of data. Files grow each day by 30 - 60 new sources/images each day. The current version of FTM is seriously limited by file size and out of memory issues.
TMG (1994 era database) can handle the information without issue, unfortunately, TMG does not link directly with Ancestry.com.