A study has found that companies with typographic logos that are intentionally missing or blanked out parts of the characters (think IBM) are perceived as less trustworthy but more innovative. "The former influence is tied to the logo's perceived clarity, while the latter influence is tied to its perceived interestingness."
Consumers with a prevention focus (?) have an overall unfavorable attitude towards the firms with incomplete logos.
Reference: Henrik Hagtvedt (2011) The Impact of Incomplete Typeface Logos on Perceptions of the Firm. Journal of Marketing: July 2011, Vol. 75, No. 4, pp. 86-93.