The class acm_proc_article_sp uses a wrong way to select fonts. The title is typeset with
\ttlfont <title text>
where \ttlfont is defined at line 320 in the .cls file by
\newfont{\ttlfnt}{phvb8t at 18pt}
The \newfont command in LaTeX has been deprecated since LaTeX2ε has been released, eighteen years ago.
You can fix this by changing the way fonts are defined:
\documentclass{acm_proc_article-sp}
\newcommand{\fixnewfont}[6]{%
% #1 = name, #2 = family, #3 = weight,
% #4 = shape, #5 = size, #6 = baselineskip
\renewcommand#1{\fontsize{#5}{#6}\usefont{\encodingdefault}{#2}{#3}{#4}}%
}
\fixnewfont{\secfnt}{ptm}{b}{n}{12}{14}
\fixnewfont{\secit}{ptm}{b}{it}{12}{14}
\fixnewfont{\subsecfnt}{ptm}{m}{it}{11}{14}
\fixnewfont{\subsecit}{ptm}{b}{it}{11}{14}
\fixnewfont{\ttlfnt}{phv}{b}{n}{18}{20}
\fixnewfont{\ttlit}{phv}{b}{sl}{18}{20}
\fixnewfont{\subttlfnt}{phv}{m}{n}{14}{20}
\fixnewfont{\subttlit}{phv}{m}{sl}{14}{20}
\fixnewfont{\subttlbf}{phv}{b}{n}{14}{20}
\fixnewfont{\aufnt}{phv}{m}{n}{12}{16}
\fixnewfont{\auit}{phv}{m}{sl}{12}{16}
\fixnewfont{\affaddr}{phv}{m}{n}{10}{12}
\fixnewfont{\affaddrit}{phv}{m}{sl}{10}{12}
\fixnewfont{\eaddfnt}{phv}{m}{n}{12}{14}
\fixnewfont{\ixpt}{ptm}{m}{n}{9}{11}
\fixnewfont{\confname}{ptm}{m}{it}{8}{10}
\fixnewfont{\crnotice}{ptm}{m}{n}{8}{10}
\fixnewfont{\ninept}{ptm}{m}{n}{9}{10.5}
\begin{document}
\title{\LaTeX{} is nice}
\maketitle
\end{document}

Don't use such a class for any other purpose than submissions that require it.
\LaTeX. Compare this against others contained in How to write (La)TeX (with parentheses) or any other TeX-related logo. Moreover,acm_proc_article-sp.clsdoes not redefine\LaTeXin any way. – Werner Jul 29 '13 at 05:52\LaTeXin a common class likearticle. The result is the same. This is the correct format for the logo. – Fran Jul 29 '13 at 05:57acm_proc_article-sp, because the same little A is obtained with all standard classes. In fact, this is not a problem at all. It should be smaller. It would be funny if LaTeX did not know how properly format your own logo. – Fran Jul 29 '13 at 07:09