Like the similar hedging phrase if you will, so to speak often appears where it adds nothing. The phrase, meaning as the saying goes or in a manner of speaking, is most useful when it indicates that an expression is not to be taken literally. Instead, many writers use so to speak to dull the impact of perfectly good expressions.
For instance, so to speak is unnecessary when the expression it refers to is obviously not meant literally. In each of these sentences, the phrase could be removed because the expression it refers to is clearly metaphorical:
The company is limping along, so to speak, for a variety of predictable business reasons. [Bloomberg]
The ripples set off by the uprising on the streets of Tunis in January have yet to reach the shore, so to speak. [BBC News]
And while agency officials expect a few hundred attendees, they’ll be keeping them on a short leash, so to speak. [Patch]
In other cases, writers use so to speak to highlight parts of their writing that they find particularly witty—for example:
One more note, so to speak, on this Super Bowl national anthem situation and we’ll be done. [Virginia Pilot]
She must also ruminate (so to speak) on the physical and psychological act of swallowing itself. [Wall Street Journal]
We can forgive these writers for taking pride in their own cleverness, but their use of so to speak comes across as desperate. If you need to highlight your wit to get it across, you’re doing something wrong.
In these sentences, so to speak is used well because there is a real chance the figurative expression referred to could be taken literally:
Rosen reports that some restaurants do quietly welcome dogs on the patio (under the table, so to speak). [Baltimore Sun]
The fish have started biting, so to speak, at the district’s annual fish sale. [Canton Repository]
The ECB should not, so to speak, print the money and let the weak countries off the hook. [Independent]