Three or more hashtags.
#[^#]+#[^#]+#
Long hashtags (15+ characters): #hashtagpunchline
#[^ ]{15}
CamelCase hashtags (3+ Words): #NotSelfAware
#[^a-z ]+[^A-Z ]+[^a-z ]+[^A-Z ]+[^a-z ]+[^ ]*
Unforgivable word shortening: I'm near ur place r u busy?
\sur\s
\sr\s
\su\s
Mass conversations (4+ Mentions): @guy @dude @otherguy @man totally.
@[^@]+@[^@]+@[^@]+@
Retweet chains (2+ RTs): OMG RT @teengirlsquad RT @beebz I'm thinking of you.
RT[^RT]+RT
Mentions with only a URL (spam): @imathis tinyurl.com/spam
^@imathis *https?://[^ ]+$
With Tweetbot you can mute Clients. So it should be possible to mute ask.fm. For example: foursquare tweets have something like "foursquare" as the application used for writing the tweet. Does that make sense?