Yes.

Any writing to flash memory has a limited lifespan.

Why do you need to keep reformatting it?

Entering data to it results in changes to the memory just the same as formatting as far as the disc is concerned.

Flash drives are very useful in taking data for viewing and processing in other computers at Browsing centers, printing centers etc. These public centers are used by many and have less control over viruses getting in to our flash drive. Anti-virus software are very subjective in removing all those viruses out there. I have seen some (relatively) cheaper anti-virus software is indicating the presence of some viruses which were not found out by standard popular anti-virus software. I think, the only positive way to eliminate the possible virus from the flash drive is to format it.

Low end anti-virus products also have a higher incidence of false positive reporting

I thought many of the more damaging virus/worm attacks could easily survive a simple format? Cleaned a friends computer once that had one in boot-sector/MBR(?) that evaded fdisk and format. Only a write protected boot floppy with a specific kill-utility was able to remove infection.

Flash drives are FAT32

Yes, but they still are very practical,useful, and inexpensive storage devices.

http://en.wikipedia.org/wiki/Flash_memory#Memory_wear

http://en.wikipedia.org/wiki/Flash_memory#Write_Endurance

I use a pin drive that has a write protect switch when working on questionable computers. That way I only write to it when I'm updating my repair software. I'm usually working on virused machines. All usb drives do wear more or less by the number of reads and writes. Most drives die from static however, not from being used.