Multiple TXT DNS records for domain

Multiple TXT DNS records are perfectly acceptable. In fact, I think one of my domains has about 6 of them. If you append it to the end of another TXT record, it is likely to stop that one performing it's correct function.

In Amazon's DNS tool, Route53, if you're trying to create multiple TXT values that share the same name, you should surround each value in quotes and separate by a carriage return.

From the Route53 docs:

A text record. Enter multiple values 
    on separate lines. Enclose text in 
    quotation marks.
Example:
    "Sample Text Entries" 
    "Enclose entries in quotation marks"