Does avast! support this Google alert or is it arbitrary just for Bit dot ly?

Read: http://www.google.com/safebrowsing/diagnostic?site=bit.ly/
and what Sucuri has to say on this: http://blog.sucuri.net/2014/10/bit-ly-blacklisted-by-google-safe-browsing.html

How trustworthy is Google Safebrowsing here and weren’t other factors weighed to bring in the block in Google Chrome.
For firefox the browser can be so configured so it won’t any longer alert these reported attack sites.

See: https://www.mywot.com/en/scorecard/Bit.ly

One comment:

The company behind this URL shortener service is legitimate but be careful of how this URL shortener is used as it is commonly used to promote malicious and misleading content.
source WOT reporter: Spam404

This does not mean that users couldn’t be advised to refrain from using any URL shortener and check any shortened URL before clicking it, and also look in the browser where the link is supposed to go when passing the mouse over over it.
For protection read: http://security.thejoshmeister.com/2009/04/how-to-preview-shortened-urls-tinyurl.html

Use: http://decryptlinks.com/ & http://longurl.org/ to pre-scan a shortened url one may not trust completely!

polonus