There are many reports from upset Google Toolbar users in the Google Web Search Help forums. The complaints all stem around the font size within the Google Toolbar.
Here is one of the complaints:
this large font is obnoxious. google please change it back or give us the option to do so if we want. pretty lame you didnt initially give us an option, let alone even a heads up.
Some of the users posted screen shots of this problem and here is one of those screen shots:

As you can see, the font size seems just a bit large for one's liking.
The thing is, Google is not fully aware of why this is happening.
Googler Kelly F. came into the thread and said:
This appears to be a hot topic! Thanks to all of you for coming to this forum to discuss it. Would you mind telling me which browsers and operating systems you're using? Any extensions or add-ons?
Shortly after, Googler Gwyneth B. came in asking for additional information. She asked, "It would also be really helpful if you all could provide screenshots of the enlarged font size you're experiencing."
So far, there is no solution posted in the forums. But if you have this issue, I'd check the thread throughout the day for updates.
Forum discussion at Google Web Search Help.

Comments:
Ekeithphillips
04/29/2011 01:31 am
I went to View, Zoom and found it at 125%. Chnging to 100% seemed to get it back to normal.
myvideotalk
05/25/2011 02:58 pm
I'm having this same problem, all my buttons are gone after I updated the toolbar, even gmail and pagerank. Is there away to to fix this, anyone?
may
05/30/2011 03:16 am
i'm having also problem regarding my web font size.the zoom button i can't find anymore
geli
05/30/2011 03:31 am
how can i get my web font size bigger.thank's
J. Fenwick
07/14/2011 02:37 pm
As other users google fonts in the toolbar is bold and large. JLF
Billie
09/23/2011 02:17 pm
my google font size is so small I can't read it
D Ann
05/21/2012 06:32 am
My font is so small I can hardly read it.